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

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = int.Parse(line[0]);
        var b = int.Parse(line[1]);
        var c = int.Parse(line[2]);
        var d = int.Parse(line[3]);
        var e = int.Parse(line[4]);
        getAns(a, b, c, d, e);
    }
    static void getAns(int a, int b, int c, int d, int e)
    {
        var x = a;
        var y = b;
        var ans = a - b;
        for (int i = 0; i <= c; i++)
        {
            var nx = a + i * d;
            var ny = b + i * e;
            ans = Max(ans, nx - ny);
        }
        Console.WriteLine(ans);
    }
}