How many ways are there to choose two distinct positive integers totaling N, disregarding the order?
import math
a = int(input())
if a%2 == 0:
    print(a/2-1)
else:
    print(math.floor(a/2))
import math
a = int(input())
if a%2 == 0:
    print(int((a/2-1)))
else:
    b = int(math.floor(a/2))
    print(b)