# coding: utf-8
import array, bisect, collections, copy, heapq, itertools, math, random, re, string, sys, time
sys.setrecursionlimit(10 ** 7)
INF = 10 ** 20
MOD = 10 ** 9 + 7


def II(): return int(input())
def ILI(): return list(map(int, input().split()))
def IAI(LINE): return [ILI() for __ in range(LINE)]
def IDI(): return {key: value for key, value in ILI()}


def read():
    x, y, d = ILI()
    return (x, y, d)


def solve(x, y, d):
    ans = 0
    if d > x + y or d < 0:
        ans = 0
    elif x <= d <= x + y:
        height = d - x
        if x >= height:
            ans = y - height + 1
        else:
            ans = x + 1
    elif 0 <= d < x:
        width = d
        if y >= width:
            ans = width + 1
        else:
            ans = y + 1

    return ans


def main():
    params = read()
    print(solve(*params))


if __name__ == "__main__":
    main()