#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<60;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int main() {
	ll A, B, T;
	cin >> A >> B >> T;
	
	ll ans = (T + A - 1) / A * A;
	
	ll t = min(T / B + 1, A);
	
	REP(b, t + 1) {
		ll a = (T - b * B + A - 1) / A;
		chmin(ans, a * A + b * B);
	}
	
	cout << ans << endl;
	
	return 0;
}