Score: 100 points
We have two distinct integers A and B.
Print the integer K such that |A - K| = |B - K|.
If such an integer does not exist, print IMPOSSIBLE
instead.
Input is given from Standard Input in the following format:
A B
Print the integer K satisfying the condition.
If such an integer does not exist, print IMPOSSIBLE
instead.
2 16
9
|2 - 9| = 7 and |16 - 9| = 7, so 9 satisfies the condition.
0 3
IMPOSSIBLE
No integer satisfies the condition.
998244353 99824435
549034394