#include<bits/stdc++.h>
using namespace std;
#define ll long long
int n;
ll a[400001],pref[400001],x,pref1[400001];
int bin(int l,int d,int i){  
	if(l==d)return l;
	if(l==d-1){
		if(pref[l]>i)
			return l;
		return d;
	}
	int mid=(l+d)/2;
	if(pref[mid]>i&&pref[mid-1]<=i)return mid;
	if(pref[mid]<=i)
		return bin(mid+1,d,i);
	return bin(l,mid-1,i);
}
ll resi(int i){
	if(pref[i]<x) 
		return -1;
	ll m=(a[i]+1)*a[i]/2ll;
	if(i==0){
		if(x>=a[0])
			return m;
		ll u=(a[0]-x)*(a[0]-x+1)/2ll;
		return m-u;
	}
	if(x==a[i]) return m;
	if(x<=a[i]){
		ll u=(a[i]-x)*(a[i]-x+1)/2ll;
		return m-u;
	}
	int mes=bin(0,i-1,pref[i]-x);
	ll trx=x-(pref[i]-pref[mes]);
	if(trx<0)return -1;  //this should not be negative but it sometimes is, i dont know why
	ll o=(a[mes]+1ll)*a[mes]/2ll,p=(a[mes]-trx)*(a[mes]-trx+1ll)/2ll;
	return pref1[i]-pref1[mes]+o-p;
}
int main(){
	cin>>n>>x;
	for(int i=0;i<n;i++)cin>>a[i];
	for(int i=n;i<2*n;i++)a[i]=a[i-n];
	n*=2;
	pref[0]=a[0];pref1[0]=a[0]*(a[0]+1)/2ll;
	for(int i=1;i<n;i++){pref[i]=pref[i-1]+a[i];pref1[i]=pref1[i-1]+a[i]*(a[i]+1)/2ll;}
	ll res=1;
	for(int i=0;i<n;i++)  //fixing the end and binary searching for the beginning
		res=max(res,resi(i));
	cout<<res;
	return 0;
}