#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int N;
long P;
main()
{
	cin>>N>>P;
	vector<int>H1(N);
	for(int&h:H1)cin>>h;
	vector<int>H2;
	for(int h:H1)
	{
		if(H2.empty()||H2.back()!=h)H2.push_back(h);
	}
	vector<int>::iterator it=H2.begin();
	while(it+1!=H2.end()&&*it>*(it+1))it++;
	vector<int>H(it,H2.end());
	long A=0,B=P;
	for(int i=1;i<H.size();i++)
	{
		long nA=9e18,nB=9e18;
		nA=min(nA,A+max(0,H[i]-H[i-1]));
		nB=min(nB,B+max(0,H[i-1]-H[i]));
		nB=min(nB,A+P);
		nA=min(nA,B+P);
		A=nA;
		B=nB;
	}
	cout<<min(A,B)<<endl;
}