#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <algorithm>
#include <functional>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cctype>
#include <string>

using namespace std;

int main() {
  int x, y, d;
  cin >> x >> y >> d;
  if (x > y) swap(x, y);
  if (x+y < d) {
    std::cout << 0 << std::endl;
  }else if (d < x){
    std::cout << d+1 << std::endl;
  }else {
    std::cout << min(x+y-d+1, x+1) << std::endl;
  }
}