# -*- coding: utf-8 -*-
"""
No.131 マンハッタン距離
https://yukicoder.me/problems/no/131

"""
import sys
from sys import stdin
input = stdin.readline


def solve(x, y, d):
    if d > x + y:
        return 0
    if d == x + y:
        return 1

    ans = 0
    if y > x:
        x, y = y, x

    if d <= y:
        ans = d + 1
    elif y <= d <= x:
        ans = y + 1
    else:
        ans = y + 1
        ans -= (d - x)
    return ans


def main(args):
    x, y, d = map(int, input().split())
    ans = solve(x, y, d)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])