#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;

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

int main(){
  ll n,k;
  cin>>n>>k;
  
  vector<ll> A(n);
  rep(i,n) cin>>A[n-i-1];
  
  ll MOD=0;
  rep(i,n) MOD+=A[i];
  
  ll t=1;
  ll ans=0;
  rep(i,n){
    ans=(ans+t*A[i])%MOD;
    t=t*k%MOD;
  }
  cout<<ans<<endl;
    
  
  return 0;
}