#include <iostream>

using lint = long long;

constexpr lint INF = 1LL << 60;

void solve() {
    lint a, b, t;
    std::cin >> a >> b >> t;

    auto ans = INF;

    if (a * a <= t) {
        for (lint y = 0; y < a; ++y) {
            if (b * y >= t) {
                ans = std::min(ans, b * y);
                break;
            }

            auto r = t - b * y;
            auto x = (r + a - 1) / a;
            ans = std::min(ans, a * x + b * y);
        }
    } else {
        for (lint x = 0;; ++x) {
            if (a * x >= t) {
                ans = std::min(ans, a * x);
                break;
            }

            auto r = t - a * x;
            auto y = (r + b - 1) / b;
            ans = std::min(ans, a * x + b * y);
        }
    }

    std::cout << ans << "\n";
}

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

    solve();

    return 0;
}