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

class Program
{
    static long NN => long.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, p) = (c[0], c[1]);
        var h = NList;
        var dp1 = 0L;
        var dp2 = long.MaxValue / 2;
        var dp3 = long.MaxValue / 2;
        for (var i = 1; i < n; ++i)
        {
            var ndp1 = Math.Min(dp1, dp2) + Math.Max(0, h[i] - h[i - 1]);
            var ndp2 = Math.Min(dp1, Math.Min(dp2, dp3)) + p;
            var ndp3 = Math.Min(dp2, dp3) + Math.Max(0, h[i - 1] - h[i]);
            dp1 = ndp1;
            dp2 = ndp2;
            dp3 = ndp3;
        }
        WriteLine(Math.Min(dp1, Math.Min(dp2, dp3)));
    }
}