#include <iostream>
using namespace std;
typedef long long ll;

const ll INF = 1000000000000000000;

int main()
{
    ll t, x, a, y, b;
    cin >> t >> x >> a >> y >> b;
    ll ans = INF;
    for(int i = 0; i <= abs(t) + a + b; i++)
    {
        ll d = t + b * i;
        if(d < 0)
        {
            continue;
        }
        int j = d / a;
        ans = min(ans, i * y + j * x + d % a);
    }
    cout << ans << endl;
}