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 ans1 = a - b;
        var ans2 = ans1 + c * (d - e);
        Console.WriteLine(Max(ans1, ans2));
    }
}