#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>

#include <algorithm>
#include <cmath>

#include <string>
#include <array>
#include <list>
#include <queue>
#include <vector>
#include <complex>
#include <set>
#include <map>

/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;

#define PII pair<int,int>
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////

int main(void){
    std::cin.tie(0); 
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    cout << setprecision(10);//

	int A,B,T;
	cin>>A>>B>>T;
	if(A>B){
		swap(A,B);
	}
	//A<=B
	int An,Bn;
	An = (T+A-1)/A;
	Bn = (T+B-1)/B;
	//int sa = B - A;
	//if(sa == 0)
	if(A==B){
		P(A*An);
		return 0;
	}
	//int now = B*Bn;
	//int BtoA = B/A;

	int Left = An;
	int ans = -1;
	
	for(int Right=0;Right <= Bn;++Right){
		while(Left*A + Right*B >= T && Left >= 0){
			if(ans == -1 || ans > Left*A + Right*B){
				ans = Left*A + Right*B;
			}
			--Left;
		}
		++Left;
		Left -= B/A;
	}
	P(ans);
    return 0;
}