#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>
#include <stack>
#include <bitset>
#include <string>
#include <cstring>
#include <iterator>
#include <random>
#include <unordered_map>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pll;
typedef long double ld;
const ll dim=1e6 + 10;
const ll mod=998244353;
const ll inf=1e18+77;
#define endl "\n"
#define fi first
#define pb push_back
#define se second
#define vll vector<ll>
ll n,t, k;
ll a[dim];
vector<pll> subs;
ll same[dim];
ll fc[dim], ufc[dim];
ll binpow(ll a, ll p){
ll r=1;
while(p>0){
if(p&1){
p--;
r*=a;
r=r%mod;
}
a=(a*a)%mod;
p/=2;
}
return r%mod;
}
ll cnt(ll k, ll n){
ll zn=(ufc[k]*ufc[n-k])%mod;
ll ch=fc[n];
ch=(ch*zn)%mod;
return ch;
}
ll f[dim];
ll b[dim];
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
//cin>>t;
fc[0]=1;
ufc[0]=1;
for(int i=1; i<=1e6; i++){
fc[i]=fc[i-1]*i;
fc[i]=(fc[i]%mod);
ufc[i]=binpow(fc[i], mod-2);
}
t=1;
while(t--){
cin>>n>>k;
for(int i=1; i<=n-k+1; i++){
cin>>a[i];
}
for(int i=1; i<=n; i++)b[i]=-1;
ll fl=1;
for(int i=2; i<=n-k+1; i++){
if(a[i]==a[i-1]){
same[i+k-1]=0;
}
else if(a[i]==a[i-1]-1){
same[i+k-1]=-1;
}
else if(a[i]==a[i-1]+1){
same[i+k-1]=1;
}
else{
fl=0;
}
}
for(int i=1; i<=k; i++){
f[i]=1;
}
for(int i=k+1; i<=n; i++){
if(same[i]==same[i-k] && same[i]!=0){
fl=0;
}
if(same[i]!=same[i-k]){
if(same[i]>same[i-k])b[i]=1;
else b[i]=0;
for(int j=i-k; j>=1 && b[j]==-1; j-=k){
b[j]=b[j+k]-same[j+k];
}
}
}
ll c=0;
for(int i=1; i<=k; i++){
if(b[i]==1)a[1]--;
if(b[i]==-1)c++;
}
if(!fl || a[1]<0){
cout<<0<<endl;
}
else{
cout<<cnt(a[1], c)<<endl;
}
}
return 0;
}
