#include <iostream>
using namespace std;
int main(){
	int x, y, d;
	cin >> x >> y >> d;
	if (d <= min(x, y)){
		cout << d + 1 << endl;
	} else if (d <= max(x, y)){
		cout << min(x, y) + 1 << endl;
	} else if (d <= x + y){
		cout << x + y + 1 - d << endl;
	} else {
		cout << 0 << endl;
	}
}