/* -*- coding: utf-8 -*-
 *
 * 131.cc: No.131 マンハッタン距離 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  int x, y, d;
  cin >> x >> y >> d;

  int minxy = min(x, y);
  int maxxy = max(x, y);

  int ans;
  if (d < minxy) ans = d + 1;
  else if (d > maxxy) ans = max(x + y - d + 1, 0);
  else ans = minxy + 1;

  printf("%d\n", ans);
  return 0;
}