#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <fstream>
#include <queue>
#include <complex>

#define INF 1145141919
#define INF_INT_MAX 2147483647
#define INF_LL_MAX 9223372036854775807
#define EPS 1e-10
#define Pi acos(-1)
#define LL long long
#define ULL unsigned long long

using namespace std;

LL A, B, T;

int main() {

	cin >> A >> B >> T;

	LL ans = INF_LL_MAX;

	for (int i = 0; i <= A && B*i <= T; i++){
		ans = min(ans, B*i + A*((T - B*i + A - 1) / A));
	}

	cout << ans << endl;

	return 0;
}