using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var t = NN;
        var c = NList;
        var (x, a) = (c[0], c[1]);
        c = NList;
        var (y, b) = (c[0], c[1]);
        WriteLine(Time(t, x, a, y, b));
    }
    static long Time(int t, long x, long a, long y, long b)
    {
        var res = t < 0 ? long.MaxValue : t;
        for (var i = 0; a * i < Math.Max(0, t) + a * b / GCD(a, b); ++i)
        {
            var j = 0L;
            if (a * i > t) j = (a * i - t + b - 1) / b;
            res = Math.Min(res, x * i + y * j + t - (a * i - b * j));
        }
        return res;
    }
    static long GCD(long a, long b)
    {
        if (a < b) return GCD(b, a);
        if (a % b == 0) return b;
        return GCD(b, a % b);
    }
}