#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll X, A, Y, B, T, ans = 1ll << 60;
    cin >> T >> X >> A >> Y >> B;
    auto f = [&](ll v){
        if(v < 0)return 1ll << 60;
        return min(v, v / A * X + v % A);
    };
    for(ll i = 0; i <= 20000000; i++){
        ans = min(ans, f(B * i + T) + i * Y);
    }
    cout << ans << '\n';
}