#include <bits/stdc++.h>

using namespace std;

int main() {
    long long b1, b2, b3;
    cin >> b1 >> b2 >> b3;

    long long ans = (b2 * (b2 - b3) + b3 * (b3 - b1)) / (b2 - b1);
    cout << ans << endl;
    return 0;
}