# -*- coding:utf-8 -*-

(x,y,d) = [int(i) for i in input().rstrip().split(" ")]

ans = 0
if d == 0:
    ans = 1
elif d == 1:
    ans = 2
elif x + y == d:
    ans = 1
elif x >= d and y >= d:
    ans = d + 1
elif x + y < d:
    ans = 0
else:
    ans = (d + 1) - max(0, d - y) - max(0, d - x)

print(ans)