#include <bits/stdc++.h>

using namespace std;
#define ll long long

int main() {
    int b1, b2, b3;
    cin >> b1 >> b2 >> b3;
    //int r=(b3-b2)/(b2-b1);
    //int d=(b1*b3-b2*b2)/(b2-b1);
    ll ans = (b2 * b2 + b3 * b3 - b1 * b3 - b2 * b3) / (b2 - b1);
    cout << ans << endl;
    return 0;
}