RT

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>
#include<map>
#include<unordered_map>
#include<vector>
#include<queue>
#include<bitset>
#include<set>
#include<ctime>
#include<random>
#define x1 xx1
#define y1 yy1
#define IOS ios::sync_with_stdio(false)
#define ITIE cin.tie(0);
#define OTIE cout.tie(0);
#define PY puts("Yes")
#define PN puts("No")
#define PW puts("-1")
#define popcount __builtin_popcount
#define int long long
using namespace std;
inline int R(){
	int x=0,f=1;int ch=getchar();
	while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
	while(isdigit(ch)){x=x*10+ch-48;ch=getchar();}return x*f;
}
inline void write(int x){
	if(x<0){x=-x;putchar('-');}
	int y=0;char z[70];
	while(x||!y){z[y++]=x%10+48;x/=10;}
	while(y--)putchar(z[y]);
}
inline void writesp(int x){
	write(x);putchar(32);
}
inline void writeln(int x){
	write(x);putchar(10);
}
#define pii pair<int,int>
#define mp make_pair
#define fi first
#define se second
#define rep(a,b,c) for(int a=b;a<=c;a++)
#define per(a,b,c) for(int a=b;a>=c;a--)
#define reprange(a,b,c,d) for(int a=b;a<=c;a+=d)
#define perrange(a,b,c,d) for(int a=b;a>=c;a-=d)
#define graph(i,j,k,l) for(int i=k[j];i;i=l[i].nxt)
#define lowbit(x) (x&-x)
#define lson(x) (x<<1)
#define rson(x) (x<<1|1)
const int maxn=5e4+5;
int n,k,a[maxn];
int lft[maxn],st[maxn],tp;//lft存决策i的左端点，st存决策点 
int f[maxn];
int calc(int l,int r){
	int tmp=r-l-1+a[r]-a[l]-k;
	return f[l]+tmp*tmp;
}
int find(int x){
	int l=1,r=tp;
	while(l<r){
		int mid=l+r+1>>1;
		if(lft[st[mid]]==x) return st[mid];
		if(lft[st[mid]]<x) l=mid;
		else r=mid-1;
	}
	return st[l];
}
signed main(){
	n=R(),k=R();rep(i,1,n)a[i]=R(),a[i]+=a[i-1];
	lft[0]=1; 
	rep(i,1,n){
		f[i]=calc(find(i),i);
		while(tp&&lft[st[tp]]>i&&calc(i,lft[st[tp]])<calc(st[tp],lft[st[tp]])) tp--;
		int l=lft[st[tp]],r=n;
		while(l<r){
			int mid=l+r>>1;
			if(calc(i,mid)<calc(st[tp],mid)) r=mid;
			else l=mid+1;
		}
		if(calc(i,l)<calc(st[tp],l)){
			st[++tp]=i;
			lft[i]=l;
		}
	}
	write(f[n]);
}