#include <iostream>
using namespace std;

int main() {
    int a, b, c;
    cin >> a >> b >> c;
    
    int x = b - a - 1;
    int d = c - b - 1;
    
    if(x > d) {
        cout << x << endl;
    }
    else {
        cout << d << endl;
    }
    return 0;
}