#include <bits/stdc++.h>
using namespace std;
#include <boost/multiprecision/cpp_int.hpp>
typedef boost::multiprecision::cpp_int mp;
int main(){
    int N,K;
    cin>>N>>K;
    vector<mp> A(N);
    mp s=0;
    for(int i=0;i<N;i++){
        cin>>A[i];
        s+=A[i];
    }
    mp ans=0;
    mp temp=1;
    for(int i=N-1;i>=0;i--){
        ans=(ans+temp*A[i])%s;
        temp=(temp*K)%s;
    }
    cout<<ans<<endl;
}