#include <iostream>
using namespace std;

int main(void) {     int max, A, B, C, diff;     cin >> A >> B >> C;     max = A;     if (B > max) max = B;     if (C > max) max = C;     diff = max * 3 - A - B - C;     if (diff % 2 == 1) cout << (diff + 3) / 2;     else cout << diff / 2;     return 0;
}