32/2= 16 games the first round
then you have 16 teams left
16/2 = 8 games the second round
8/2 =4 teams left
4/2 =2 games the 3rd round
then you have 2 teams left, so 1 game in the fourth round
so 16 +8 +4 +2 +1 = 31 games
