#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001LL

int main(){
	
	long long n,m;
	cin>>n>>m;
	vector<long long> a(n);
	rep(i,n)cin>>a[i];
	mint ans = mint(m).pow(n);
	rep(i,n){
		ans += mint(m).pow(n-1) * (m-a[i]);
	}
	a.push_back(m);
	vector<mint> dp(4);
	dp[0] = 1;
	rep(i,n){
		vector<mint> ndp(4,0);
		rep(j,4){
			rep(k,4){
				int l = 1,r = m;
				rep(ll,2){
					if((0==((k>>ll)&1))){
						r = min(r,(int)a[i+ll]);
					}
					else{
						l = max(l,(int)a[i+ll]+1);
					}
				}
				if(r-l+1<=0)continue;
				if(i==0){
					ndp[k] += dp[j] * (r-l+1);
				}
				else{
					
					rep(ll,2){
						int tr = r,tl = l;
						if(ll==0)tr = min(tr,(int)a[i-1]);
						else tl = max(tl,(int)a[i-1]+1);
						if(tr-tl+1<=0)continue;
						int x = 0,y = 0;
						if(j&1)x++;
						if(k&1)x++;
						if(j&2)y++;
						if(ll)y++;
						if(x<y)continue;
						ndp[k] += dp[j] * (tr-tl+1);
					}
				}
			}
		}
		swap(dp,ndp);
	}
	rep(i,4)ans -= dp[i];
	cout<<ans.val()<<endl;
	return 0;
}