#include <iostream>
using namespace std;
#define out(v) cout<<v<<"\n"

int main() {
  cin.tie(0); ios::sync_with_stdio(false);
  int x, y, d;
  cin >> x >> y >> d;

  if (d <= min(x, y)) {
    out(d+1);
  } else if (min(x, y) <= d && d <= max(x, y)) {
    out(min(x, y)+1);
  } else if (max(x, y) <= d) {
    out(max(0, x + y - d + 1));
  }

  return 0;
}