#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cmath>
#include <iomanip>
#include <map>
using namespace std;
typedef long long LL;

int main(){
    LL A, B, T;
    cin >> A >> B >> T;
    if(A > B) swap(A, B);
    LL bc = (T + B-1) / B;
    LL ans = (1LL<<60);
    for(LL i = 0; i <= A; i++){
        if(bc - i < 0) break;
        LL ac = (max<LL>(0, T - (bc-i)*B) + A - 1) / A;
        ans = min(ans, A*ac + B*(bc-i));
    }
    cout << ans << endl;
    return 0;
}