#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = uint32_t;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

int main() {
    const int M = 30000;
    ll a, b, t;
    cin >> a >> b >> t;
    if(b >= M){
        ll ans = (t+b-1)/b*b;
        for (int i = 0; i <= t; i += b) {
            ans = min(ans, i+(t-i+a-1)/a*a);
        }
        cout << ans << "\n";
    }else {
        ll ans1 = t/(2*a*b)*2*a*b, ans2 = INF<ll>; t %= (2*a*b);
        vector<ll> v(b+1), u(a+1);
        for (int i = 0; i <= b; ++i) {
            v[i] = i*a;
        }
        for (int i = 0; i <= a; ++i) {
            u[i] = i*b;
        }
        int cur = b;
        for (int i = 0; i <= a; ++i) {
            while(cur > 0 && u[i]+v[cur-1] >= t) cur--;
            if(u[i]+v[cur] >= t) ans2 = min(ans2, u[i]+v[cur]);
        }
        cout << ans1+ans2 << "\n";
    }
    return 0;
}