Code:

#include<bits/stdc++.h>
#define int long long 
using namespace std;
const int MAXN=1e6+5;
const int mod=998244353;
int a[MAXN],qzh[MAXN],qzh2[MAXN];
signed main(){
	int n,k,ans=0,cnt=1;
	scanf("%lld%lld",&n,&k);
	for(int i=1;i<=n;++i){
		scanf("%lld",&a[i]);
		qzh[i]=qzh[i-1]+a[i];
		qzh2[i]=qzh2[i-1]+a[i]*a[i];
	}
	for(int i=1;i<=k;++i){
		while((a[cnt]+1)*(a[cnt]+1)>(a[cnt]+i)*(a[cnt]+i)&&cnt<n)cnt++;
		cnt--;
		ans=(ans+qzh2[cnt]+(2*qzh[cnt])%mod+cnt)%mod;
		ans=(ans+qzh2[n]-qzh2[cnt]+(2*i*(qzh[n]-qzh[cnt]))%mod+((n-cnt)*(i*i)%mod)%mod)%mod;
	}
	printf("%lld",ans);
	return 0;
}
/*
(a1+i)^2+(a2+i)^2+(an+i)^2
=a1^2+a2^2+an^2+2*i*(a1+a2+an)+(i^2)*n
*/