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

int main()
{
	unsigned 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;
	}
	return 0;
}