#include <cstdio>
#include <iostream>
#include <algorithm>
using namespace std;
long long x,y,d;
int main(void){
  cin >> x >> y >> d;
  if(x > y) swap(x,y);

  if(d <=x) cout << d+1 << endl;
  else if(x < d && d <= y) cout << x+1 << endl;
  else cout << max(0LL,x+y-d+1) << endl;
}