#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>

using namespace std;

int main() {
	int x, y, d;

	cin >> x >> y >> d;

	int ans = 0;
	int xx, yy;

	for (int i = 0; i <= d; i++) {
		xx = d - i;
		yy = i;
		if (0 <= xx && xx <= x && 0 <= yy && yy <= y) {
			ans++;
		}
	}
	cout << ans << endl;
	return 0;
}