#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

int main(){
    ll T;
    cin >> T;

    ll X, A;
    cin >> X >> A;

    ll Y, B;
    cin >> Y >> B;

    ll ans = INF;
    for(ll r=0; r<=1e7; r++){
        ll S = T + r*B;
        if(S < 0) continue;
        ll q = S/A;
        ll p = S%A;
        ans = min(ans, p+q*X+r*Y);
    }

    cout << ans << endl;
}