#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=2e5+99;
int n,m,a[N],ans;
struct node{
	int sum,len;
	int l,r;
	bool operator <(const node&A) const{
		return sum*A.len<A.sum*len;
	}
	bool operator !=(const node&A) const{
		return sum!=A.sum||len!=A.len||l!=A.l||r!=A.r;
	}
	node operator +(const node&A){
		return (node){sum+A.sum,len+A.len,min(l,A.l),max(r,A.r)};
	}
};
node sta1[N],sta2[N];
int cnt1,cnt2;
int seq[N],cnt;
void solve(){
	int re=n*(m+1);
	for(int i=1;i<=n;i++)
		re-=seq[i]*(n-i);
	ans=max(ans,re);
	return;
}
priority_queue<node> que;
node nd[N];
int f[N];
int find(int x){ if(f[x]==x) return x; return f[x]=find(f[x]); }
void merge(int x,int y){//
	f[x]=y;
	nd[y]=nd[y]+nd[x];
	que.push(nd[y]);
	return;
}
void merge1(){
	for(int i=1;i<=n+1;i++)
		f[i]=i,nd[i]=(node){-a[i],1,i,i};
	for(int i=1;i<=n+1;i++)
		que.push(nd[i]);
	node now;
	int x,y;
	while(!que.empty()){
		now=que.top(); que.pop();
		if(nd[find(now.l)]!=now) continue;
		if(now.l==1) continue;
		x=find(now.l); y=find(now.l-1);
		if(nd[x]<nd[y]) continue;//-
		merge(x,y);
	}
	for(int i=n+1;i>=1;i--)
		if(f[i]==i)
			sta1[++cnt1]=nd[i],sta1[cnt1].sum=-sta1[cnt1].sum;
	return;
}
void merge2(){
	for(int i=1;i<=n+1;i++)
		f[i]=i,nd[i]=(node){-a[i],1,i,i};
	for(int i=1;i<=n+1;i++)
		que.push(nd[i]);
	node now;
	int x,y;
	while(!que.empty()){
		now=que.top(); que.pop();
		if(nd[find(now.r)]!=now) continue;
		if(now.r==n+1) continue;
		x=find(now.r); y=find(now.r+1);
		if(nd[x]<nd[y]) continue;//-
		merge(x,y);
	}
	for(int i=1;i<=n+1;i++)
		if(f[i]==i)
			sta2[++cnt2]=nd[i],sta2[cnt2].sum=-sta2[cnt2].sum;
	return;
}
signed main(){
	std::ios::sync_with_stdio(false);
	cin.tie(0);
	cin>>n>>m;
	for(int i=1;i<=n;i++) cin>>a[i];
	sort(a+1,a+n+1); a[n+1]=m+1;
	for(int i=n+1;i>=1;i--) a[i]-=a[i-1];
	node now;
	merge1();
	merge2();
//	cout<<cnt1<<endl;
//	for(int i=cnt1;i>=1;i--)
//		cout<<sta1[i].l<<" "<<sta1[i].r<<endl;
//	cout<<cnt2<<endl;
//	for(int i=cnt2;i>=1;i--)
//		cout<<sta2[i].l<<" "<<sta2[i].r<<endl;
	int l=1,r=n+1;
	while(cnt1&&cnt2){
		if(sta1[cnt1].r>=sta2[cnt2].l) break;
		if(sta1[cnt1]<sta2[cnt2]){
			while(l<=sta1[cnt1].r)
				seq[++cnt]=a[l++];
			cnt1--;
		}
		else{
			while(r>=sta2[cnt2].l)
				seq[++cnt]=a[r--];
			cnt2--;
		}
	}
//	cout<<l<<" "<<r<<endl;
	for(int i=l;i<=r;i++)
		seq[cnt+i-l+1]=a[i];
	solve();
	for(int i=r;i>=l;i--)
		seq[cnt+r-i+1]=a[i];
	solve();
	cout<<ans;
	return 0;
}