#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef float fl;
typedef double dou;
typedef long double ld;
#define register int ri;

const ll inf = 1e9;
const ll inf_common = 0x3f3f3f3f;
const ll inf_larger = 0x7fffffff;
const ll inf_ll = 1e18;
const ll mod = 998244353;
const dou eps = 1e-6;

inline ll read()
{
	ll ans = 0;
	ll f = 1;
	char c = getchar();
	
	while( c < '0' || c > '9' )
	{
		if( c == '-' )
		{
			f = -1;
		}
		
		c = getchar();
	}
	
	while( c >= '0' && c <= '9' )
	{
		ans = ( ans << 3 ) + ( ans << 1 ) + ( c - 48 );
		c = getchar();
	}
	
	return ans * f;
}

inline void write( ll x )
{
	if( x < 0 )
	{
		putchar( '-' );
		x = -x;
	}
	
	if( x > 9 )
	{
		write( x / 10 );
	}
	
	putchar( x % 10 + '0' );
}

ll a[1000001] = {0};
ll b[1000001] = {0};

int main()
{
	ll n = read();
	ll k = read();
	ll i = 0;
	ll pos = 0;
	ll sum = 0;
	ll ans = 0;
	bool flag = 0;
	
	for( i = 1 ; i <= n ; i++ )
	{
		a[i] = read();
		
		if( a[i] >= 0 && !flag )
		{
			flag = 1;
			pos = i - 1;
		}
		
		a[i] %= mod;
		
		b[i] = b[i - 1] + a[i];
		b[i] %= mod;
		
		sum += ( a[i] + 1 ) * ( a[i] + 1 );
		sum %= mod;
	}
	
	ans = sum;
	
	for( i = 2 ; i <= k ; i++ )
	{
		sum %= mod;
		sum += ( ( ( b[n] - b[pos] ) % mod * 2 ) % mod + ( ( n - pos ) % mod ) * ( ( 2 * i - 1 ) % mod ) ) % mod;
		
		sum %= mod;
		
		while( pos )
		{
			if( a[pos] + i <= 0 )
			{
				break;
			}
			
			sum += ( a[pos] * a[pos] ) + 1 % mod;
			
			sum %= mod;
			
			pos--;
		}
		
		ans += sum % mod;
		ans %= mod;
	}
	
	write( ans );
	
	return 0;
}