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

class Program
{
    static int[] NList => ReadLine().TrimStart().Split().Select(int.Parse).ToArray();
    static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray();
    static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var p = NList;
        var (a, b, c, d, e) = (p[0], p[1], p[2], p[3], p[4]);
        WriteLine(Math.Max(a - b, a - b + c * (d - e)));
    }
}