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

using ll = long long;
#define rep(i, n) for(int i = 0; i < n; i++)

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