#include<iostream>
#include<cstdio>
#include<algorithm>
#define N 50003
#define M 5
using namespace std;
int read()
{
	char c=0;
	int sum=0;
	while (c<'0'||c>'9') c=getchar();
	while ('0'<=c&&c<='9') sum=sum*10+c-'0',c=getchar();
	return sum;
}
const long long inf=(long long)(1e18);
struct reads
{
	int a,b,data;
	bool operator < (const reads &t)const
	{
		return data<t.data;
	}
};
reads st[N*M+1],st2[N*M+1];
int n,L,p[N+1],length,length2;
long long ans,DP[N+1][M+1],dp[N+1][M+1][M+1],delta[N+1][M+1];
void solve(int l,int r)
{
	if (l==r) return;
	int mid=(l+r)>>1,ps;
	long long minn;
	solve(l,mid),length=length2=0;
	for (int i=l;i<=mid;++i)
		for (int j=0;j<=L;++j)
			st[++length]=(reads){i,j,p[i-1]-j};
	for (int i=mid+1;i<=r;++i)
		for (int j=0;j<=L;++j)
			st2[++length2]=(reads){i,j,p[i]-j};
	sort(st+1,st+length+1),sort(st2+1,st2+length2+1);
	for (int i=0;i<=L;++i)
	{
		for (int j=l;j<=r;++j)
			for (int k=0;k<=L;++k)
				DP[j][k]=inf;
		DP[mid][i]=0;
		for (int j=mid-1;j>=l;--j)
		{
			ps=L+1,minn=inf;
			for (int k=L;k>=0;--k)
			{
				while (ps-1>=0&&p[j+1]-(ps-1)<=p[j]-k) --ps,minn=min(minn,DP[j+1][k]-(p[j+1]-ps));
				DP[j][k]=min(DP[j][k],minn+(p[j]-k));
			}
			ps=-1,minn=inf;
			for (int k=0;k<=L;++k)
			{
				while (ps+1<=L&&p[j+1]-(ps+1)>p[j]-k) ++ps,minn=min(minn,DP[j+1][k]+(p[j+1]-ps));
				DP[j][k]=min(DP[j][k],minn-(p[j]-k));
			}
		}
		for (int j=mid+1;j<=r;++j)
		{
			ps=L+1,minn=inf;
			for (int k=L;k>=0;--k)
			{
				while (ps-1>=0&&p[j-1]-(ps-1)<=p[j]-k) --ps,minn=min(minn,DP[j-1][k]-(p[j-1]-ps));
				DP[j][k]=min(DP[j][k],minn+(p[j]-k));
			}
			ps=-1,minn=inf;
			for (int k=0;k<=L;++k)
			{
				while (ps+1<=L&&p[j-1]-(ps+1)>p[j]-k) ++ps,minn=min(minn,DP[j-1][k]+(p[j-1]-ps));
				DP[j][k]=min(DP[j][k],minn-(p[j]-k));
			}
		}
		ps=0,minn=inf;
		for (int j=1;j<=length2;++j)
		{
			while (ps+1<=length&&st[ps+1].data<=st2[j].data)
			{
				++ps;
				for (int k=0;k<=L;++k) minn=min(minn,dp[st[ps].a][st[ps].b][k]+DP[st[ps].a][k]-st[ps].data);
			}
			for (int k=0;k<=L;++k) dp[st2[j].a][k][st2[j].b]=min(dp[st2[j].a][k][st2[j].b],minn+DP[st2[j].a-1][k]+st2[j].data);
		}
		ps=length+1,minn=inf;
		for (int j=length2;j>=1;--j)
		{
			while (ps-1>=1&&st[ps-1].data>st2[j].data)
			{
				--ps;
				for (int k=0;k<=L;++k) minn=min(minn,dp[st[ps].a][st[ps].b][k]+DP[st[ps].a][k]+st[ps].data);
			}
			for (int k=0;k<=L;++k) dp[st2[j].a][k][st2[j].b]=min(dp[st2[j].a][k][st2[j].b],minn+DP[st2[j].a-1][k]-st2[j].data);
		}
	}
	solve(mid+1,r);
	return;
}
int main()
{
	n=read()+1,L=read(),p[0]=p[1]=0,ans=inf;
	for (int i=1;i<=n;++i)
	{
		for (int j=0;j<=L;++j)
			for (int k=0;k<=L;++k)
				dp[i][j][k]=inf;
		for (int j=0;j<=L;++j) delta[i][j]=inf;
	}
	dp[1][0][0]=0;
	for (int i=2;i<=n;++i) p[i]=read();
	solve(1,n);
	for (int i=1;i<=n;++i)
	{
		for (int j=0;j<=L;++j)
			for (int k=0;k<=L;++k)
				delta[i][k]=min(delta[i][k],dp[i][j][k]);
		if (i!=1)
		{
			for (int j=0;j<=L;++j)
				for (int k=0;k<=L;++k)
					delta[i][j]=min(delta[i][j],delta[i-1][k]+abs((p[i]-j)-(p[i-1]-k)));
		}
	}
	for (int i=0;i<=L;++i) ans=min(ans,delta[n][i]);
	printf("%lld\n",ans);
	return 0;
}