import java.util.*;

class Main {
    static final long I=1L<<50;
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n=Integer.parseInt(scan.next());
        long p=Integer.parseInt(scan.next());
        long[] h=new long[n];
        for(int i=0;i<n;++i)
            h[i]=Integer.parseInt(scan.next());
        long[] l=new long[n],r=new long[n];
        l[0]=r[n-1]=0;
        for(int i=1;i<n;++i)
            l[i]=l[i-1]+Math.max(h[i]-h[i-1],0);
        for(int i=n-2;i>=0;--i)
            r[i]=r[i+1]+Math.max(h[i]-h[i+1],0);
        MaxSegmentTree s1=new MaxSegmentTree();
        MaxSegmentTree s2=new MaxSegmentTree();
        long[] dp=new long[n];
        dp[0]=0;
        s1.update(0,l[0]);
        s2.update(0,-r[0]);
        for(int i=1;i<n;++i){
            long m=l[i];
            m=Math.min(m,-s1.query(0,i)+l[i]+p);
            m=Math.min(m,-s2.query(1,i)-r[i]+p);
            dp[i]=m;
            s1.update(i,-m+l[i]);
            s2.update(i,-m-r[i]);
        }
        System.out.println(dp[n-1]);
    }
}
class MaxSegmentTree {
    static final int SIZE = 1 << 18;
    static final long INFINITY = (1L << 61) - 1;
    long[] seg;
    MaxSegmentTree() {
	this.seg = new long[2 * SIZE];
    }
    void update(int x, long value) {
	x += SIZE - 1;
	this.seg[x] = value;
	while (x > 0) {
	    x = (x - 1) / 2;
	    this.seg[x] = Math.max(this.seg[2 * x + 1], this.seg[2 * x + 2]);
	}
    }
    long query(int l, int r) {
	l += SIZE - 1;
	r += SIZE - 1;
        long y = -INFINITY;
	while (l < r) {
	    if ((l & 1) == 0) {
		y = Math.max(y, this.seg[l]);
	    }
	    if ((r & 1) == 0) {
		y = Math.max(y, this.seg[r - 1]);
	    }
	    l /= 2;
	    r = (r - 1) / 2;
	}
	return y;
    }
}