#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<list>
#include<algorithm>
#include<utility>
#include<complex>

using namespace std;

#define reE(i,a,b) for(auto (i)=(a);(i)<=(b);(i)++)
#define rE(i,b) reE(i,0,b)
#define reT(i,a,b) for(auto (i)=(a);(i)<(b);(i)++)
#define rT(i,b) reT(i,0,b)
#define rep(i,a,b) reE(i,a,b);
#define rev(i,a,b) for(auto (i)=(b)-1;(i)>=(a);(i)--)
#define fe(i,b) for (auto &(x):b);
#define itr(i,b) for(auto (i)=(b).begin();(i)!=(b).end();++(i))
#define rti(i,b) for(auto (i)=(b).rbegin();(i)!=(b).rend();++(i))
#define LL long long
#define all(b) (b).begin(),(b).end()

#define input_init stringstream ss; string strtoken, token; istringstream is
#define input_line  getline(cin, strtoken);is.str(strtoken);is.clear(istringstream::goodbit)
#define input_token(num) ss.str(""); ss.clear(stringstream::goodbit); getline(is, token, ','); ss << token; ss >> num

#define dir(xx,yy,x,y,i) (xx)=(x)+dir[(i)],(yy)=(y)+dir[(i)+1]

typedef complex<double> P;
typedef vector<P> Poly;

const LL INF = 1 << 30;
const double eps = 1e-8;
const int dir[] = { 0, 1, 0, -1, 0 };

int main(void){
	LL a, b,A,B,T;
	cin >> A >> B >> T;

	a = 0;
	b = T / B;
	if (b*B < T)b++;
	LL res=b*B;
	while (b > 0){
		LL d = a*A+b*B - T;
		b -= d / B;
		while (b>0&&a*A + b*B >= T)b--;
		d = a*A + b*B - T;
		a += d / A;
		while (a*A + b*B < T)a++;
		res = min(res, a*A + b*B);
	}

	cout << res << endl;
	return(0);
}