#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;




int main() {
	int a, b, c;
	cin >> a >> b >> c;
	int num = abs(a - c);
	if (max(a, c) - num < b) num = b - min(a, c) - 1;
	if ((a > b > c) || (a < b < c)) cout << "0" << endl;
	
	else cout << num << endl;

	return 0;
}