#include <bits/stdc++.h>
using namespace std;
using LL=long long;
template<class T>void sort(vector<T> &v){sort(v.begin(),v.end());}
template<class T>int lower_bound(vector<T> &v, T key){
	return distance(v.begin(), lower_bound(v.begin(),v.end(),key));
}
template<class T>int upper_bound(vector<T> &v, T key){
	return distance(v.begin(), upper_bound(v.begin(), v.end(), key));
}

int main(){
	const int mod=1000000007;
	int n,p;cin>>n>>p;
	vector<LL> a(n);for(auto &i:a)cin>>i;

	a[0]=0;a[1]=1;
	for(int i=2;i<n;i++)a[i]=(p*a[i-1]+a[i-2])%mod;

	LL sum=0;for(auto i:a)sum=(sum+i)%mod;
	LL tr=0;for(auto i:a)tr=(tr+i*i)%mod;

	LL ans=0;
	ans=sum*sum-tr;
	if(ans%2==1)ans+=mod;
	ans/=2;
	ans+=tr;
	ans%=mod;
	cout<<ans<<endl;
	return 0;
}