It was never going to be easy.
With 24 teams in the group stages at Euro 2016, that does not divide neatly into 16 qualifying for the knockout stages.
The tournament will need a helping hand from Uefa in the guise of having the best four third-placed teams from the six groups progressing to the last 16.
BSports helps explain which sides can go through, why yellow cards could prove crucial, and who is in pole position in the 'third-place table'.
- Check out all the tables, results and fixtures - and plot each side's route to the final
Group-by-group: Who is going through and who is going home?
Group A
Host nation France finished as group winners on seven points. Switzerland, who drew 0-0 with France in their final group game, were second on five points.
Albania beat Romania 1-0 on Sunday, their first win at a major tournament. They now face a three-day wait to find out if they will progress to the last 16 as one of the best third-place sides.
Group B
England will win the group if they beat Slovakia, and will qualify even with a draw. However, in that instance they will be knocked off top spot if Wales beat Russia. If England lose, they could finish as low as third.
Wales will go through with victory against Russia, who are bottom of the group but could still qualify with a win. A draw would be enough for Wales if Slovakia do not beat England. If Wales lose, they may finish bottom.
Group C
Group leaders Germany are likely to qualify even if they lose to Northern Ireland - because they are on four points and cannot finish bottom of the group.
With three points, Northern Ireland top the third-place finishers at the moment - and they will go through if they beat Germany. A draw would be enough for second place if Ukraine beat Poland, and Michael O'Neill's side could even progress if they lose.
Poland will go through if they beat Ukraine, who were the only team to be knocked out after two games.
Group D
Spain are through but will finish second if they are beaten by Croatia, who need only a draw to ensure progression.
Should Croatia lose, the Czech Republic will finish level with them on four points if they beat Turkey, with goal difference or disciplinary records likely to decide who takes second spot. Turkey will finish third if they win.
Group E
Italy have already secured their place in the last 16 and are guaranteed group winners, while Belgium, Sweden and the Republic of Ireland will contest second and third places.
The Republic must win to stand any chance of qualifying, although Martin O'Neill's team - currently bottom of the table - may have to settle for third place if Belgium beat Sweden. The winners of the Belgium-Sweden game will go through as runners-up.
Group F
Many expected Portugal to top this group but they are currently third, without a win in two games. If they beat Hungary they will be guaranteed a top-two finish, while a point for Hungary would be enough to see them through.
Iceland could top the group if they beat bottom-placed Austria, and will progress if they match or better Portugal's result.
However, goals and disciplinary records could yet come into play here. More on that now...
What happens if teams finish level on points?
The top two teams from each group qualify automatically for the last 16, but how are sides separated if they finish on the same number of points?
The final position of teams will be decided by these criteria, in the following order:
- Head-to-head record in the group
- Points in the match(es) between the teams in question
- Goal difference in those matches
- Goals scored in those matches
- If teams still have an equal ranking, the criteria are reapplied but only to matches between the teams in question to determine their final rankings. This only applies if there are more than two teams level on points
- If teams are still level, it comes down to goal difference in all group matches, followed by goals scored, fair play conduct in the group stage, and finally Uefa national team coefficient rankings
Who is likely to finish third in each group?
Group A: Albania beat Romania on Sunday to secure third spot.
Group B: Slovakia are currently third and must get a better result against England than Wales manage against Russia in order to climb higher. If Slovakia and Wales both win, England will slip to third, while Russia must beat Wales to get into the top three.
Group C: If Northern Ireland draw with Germany and Poland lose to Ukraine, both Northern Ireland and Poland would have four points. However, Poland's 1-0 victory over Michael O'Neill's men would ensure Northern Ireland finish third.
Group D: Whoever wins the game between third-placed Czech Republic and Turkey in fourth will finish no lower than third. Turkey must win or will go out, while a draw guarantees the Czech Republic third place. Only if the Czech Republic win and second-placed Croatia lose to Spain does it get complicated. Croatia and the Czech Republic be level on four points and head-to-head following their 2-2 draw. If their goals scored and conceded are level, the Czechs would progress via fair play as it stands - they have been shown two yellow cards compared to Croatia's four.
Group E: One of Republic of Ireland, Sweden or Belgium. Republic of Ireland must get a better result against Italy than Sweden manage against Belgium. If Ireland and Sweden both win, Sweden finish second, the Republic third and Belgium go out. If Ireland and Sweden both lose, Sweden will stay third and the Republic will be knocked out. Belgium will finish third if they lose to Sweden and the Republic do not beat Italy.
Group F: Portugal are currently third and will probably stay there unless they beat group leaders Hungary. If Portugal do win, Hungary will be relying on the result of the game between Iceland and Austria; an Iceland win would relegate Hungary to third; a draw would leave Iceland third; while an Austria win would keep Hungary second and send Iceland out.
What about that third-placed table?
We know that the top two teams go through, but what happens to those third-placed teams? Remember only four can go through from six.
The following Uefa criteria will be applied, in this order:
- Points tally
- Goal difference
- Goals scored
- Fair play ranking in the group stage
- Uefa national team coefficient rankings (These are based on all competitive results since September 2010. England are ranked third overall but Republic of Ireland are 20th of the 24 finalists, Wales are 22nd and Northern Ireland 24th)
Who will the third-placed teams play in the last 16?
Here's a Uefa's graphic to help explain which third-placed teams will face which group winners:
