#include <iostream>
#include <vector>

using lint = long long;

void solve() {
    std::vector<lint> xs(3);
    for (auto& x : xs) std::cin >> x;

    std::cout << (xs[2] - xs[1]) * (xs[2] - xs[1]) / (xs[1] - xs[0]) + xs[2]
              << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}