#include<iostream>
#include<algorithm>
using namespace std;


long long A, B, T;

void read() {
    cin >> A >> B >> T;
}


void work() {
    int bgnNB = (T + B - 1) / B;
    int endNB = max(0LL, bgnNB - A);
    long long minV = 1LL << 60;
    
    for (int nB = bgnNB; nB >= endNB; --nB) {
        int remainT = T - nB * B;
        int nA = max(0LL, remainT + A - 1) / A;
        minV = min(minV, nA * A + nB * B);
    }
    
    cout << minV << endl;
}


int main() {
    read();
    work();
    return 0;
}