#include <bits/stdc++.h>
using namespace std;

int main() {
  int x,y,d;
  cin >> x >> y >> d;
  if(x+y<d) cout << 0 << endl;
  else cout << d+1-(max(x,d)-x+max(y,d)-y) << endl;
  //cout << max(0,d+1-max(x,d)+x-max(y,d)+y) << endl;
  return 0;
}