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

#define REP(i,s,n) for(int i=(int)(s);i<(int)(n);i++)

using namespace std;
typedef long long int ll;
typedef vector<int> VI;
typedef pair<int, int> PI;
const double EPS=1e-9;

ll a, b, t;

ll f(ll v) {
  ll res = a * v + max((t - a * v + b - 1) / b * b, 0LL);
	cerr << "f(" << v<< ")=" << res << endl;
	return res;
}

int main(void){
  cin >> a >> b >> t;
	if (a < b) { swap(a, b); }
  ll x = 0, y = 1LL << 33;
  while (y - x >= 10) {
    ll z = (2 * x + y) / 3;
    ll w = (x + 2 * y) / 3;
    if (f(z) < f(w)) {
      y = w;
    } else {
      x = z;
    }
		cerr << "x="<<x<<",y="<<y<<endl;
  }
  ll mi = f(x);
  REP(i, x, y + 1) {
    mi = min(mi, f(i));
  }
  cout << mi << endl;
}