#if !__INCLUDE_LEVEL__
    #include __FILE__

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll T, X, A, Y, B;
    cin >> T >> X >> A >> Y >> B;

    if (T > 0) {
        if (X >= A) {
            cout << T << "\n";
            return 0;
        }

        ll TT = T % A;
        ll ans = T / A * X;
        cerr << ans << "\n";
        ll add_cost = TT;
        REP(i, 1e7) {
            if (i == 0)
                continue;
            ll cost = X * i;
            if ((A * i - TT) % B == 0) {
                cost += Y * (A * i - TT) / B;
            } else {
                cost += Y * ((A * i - TT) / B + 1) + ((A * i - TT) % B);
            }
            add_cost = min(add_cost, cost);
        }

        cout << ans + add_cost << "\n";
    } else {
        if (T % B == 0) {
            cout << T / B * Y << "\n";
            return 0;
        }
        T *= -1;
        ll TT = (T / B + 1) * B - T;
        ll ans = (T / B + 1) * Y;
        cerr << (T / B + 1) * B << "\n";
        ll add_cost = TT;
        REP(i, 1e7) {
            // if (i == 0)
            //     continue;
            if (TT + B * i < A)
                continue;

            ll cost = Y * i;

            if ((B * i + TT) % A == 0) {
                cost += X * (B * i + TT) / A;
            } else {
                cost += X * (B * i + TT) / A + ((B * i + TT) % A);
            }
            add_cost = min(add_cost, cost);
        }

        cout << ans + add_cost << "\n";
    }

    return 0;
}

//====================temp====================
#else
    #include <bits/stdc++.h>
using namespace std;
    #define REP(i, n) for (int i = 0; i < (int)(n); i++)
    #define RREP(i, n) for (int i = ((int)(n)-1); i >= 0; i--)
    #define REPITR(itr, ARRAY) \
        for (auto itr = (ARRAY).begin(); itr != (ARRAY).end(); ++itr)
    #define RREPITR(itr, ARRAY) \
        for (auto itr = (ARRAY).rbegin(); itr != (ARRAY).rend(); ++itr)
    #define ALL(n) (n).begin(), (n).end()
using ll = long long;
using ull = unsigned long long;
//#define int long long
template<typename T> struct edge {
    int to;
    T cost;
    edge() {}
    edge(int to, T cost): to(to), cost(cost) {}
};
#endif