#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

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