/* -*- coding: utf-8 -*-
 *
 * 176.cc: No.176 2種類の切手 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

typedef long long ll;
const ll LINF = 1LL << 60;

/* typedef */

typedef vector<int> vi;
typedef queue<int> qi;
typedef pair<int,int> pii;

/* global variables */

/* subroutines */

/* main */

// a*x+b*y >= t
// x >= (t-b*y)/a

int main() {
  ll a, b, t;
  cin >> a >> b >> t;

  ll minsum = LINF;
  for (ll y = 0;; y++) {
    ll x = (t - b * y + a - 1) / a;
    ll sum = a * x + b * y;
    if (minsum > sum) minsum = sum;
    if (b * y > t || y > a) break;
  }

  printf("%lld\n", minsum);
  return 0;
}