ore2

#include<stdio.h>
#include<queue>
#include<deque>
using namespace std;
typedef long long int ll;
ll const inf = 1e18;
int const N = 1000010;
int n;
ll k;

inline ll max(ll a,ll b){
    return (a > b ? a : b);
}



ll qs[N];
ll arr[N];
ll dp[N];

int main()
{
    scanf("%d %lld",&n,&k);
    for(int i = 1 ; i <= n ; i++){
        scanf("%lld",&arr[i]);
        qs[i] = qs[i-1] + arr[i];
    }
    dp[0] = 0;

    priority_queue<pair<ll,int> > pq;
    pq.push({0,0});

    deque<pair<ll,int> > dq;
    dq.push_back({0,0});

    //bottom up
    for(int i = 1 ; i <= n ; i ++){
    //  while(!pq.empty() && pq.top().first - dp[pq.top().second - 1] + qs[i] > k)pq.pop();

        while(!dq.empty() && dq.front().first - dp[dq.front().second - 1] + qs[i] > k)dq.pop_front();

    //  dp[i] = max(dp[i-1] ,pq.empty() ? 0 : pq.top().first + qs[i]);

        dp[i] = max(dp[i-1] , dq.empty() ? 0 : dq.front().first + qs[i]);

    //  pq.push({dp[i-1]-qs[i],i});

        while(!dq.empty() && dq.back().first < dp[i-1]-qs[i])dq.pop_back();
        dq.push_back({dp[i-1]-qs[i],i});
    }
    printf("%lld",dp[n]);
    return 0;
}