#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int num[310];
ll dp[310][310];
int main(){
    int n,h;scanf("%d%d",&n,&h);
    memset(dp,0x3f,sizeof(dp));
    for(int i=1;i<=n;i++)
    scanf("%d",&num[i]),dp[i][i]=h;
    for(int i=n;i;i--)
    for(int j=i+1;j<=n;j++)
    for(int k=i;k<j;k++)
    dp[i][j]=min(dp[i][j],dp[i][k]+dp[k+1][j]-max(0,h-(num[j]-num[i]-1)/2));
    printf("%lld",dp[1][n]);
}