#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)

int main(){
    int n,k;
    cin>>n>>k;
    vector<int>a(n);
    ll wa=0;
    rep(i,n){
        cin>>a[i];
        wa+=a[i];
    }
    ll sum=0;
    ll bai=1;
    rep(i,n){
        sum+=bai*a[n-i-1];
        sum%=wa;
        bai*=k;
    }
    ll ans=sum%wa;
    //cout<<sum<<endl;
    cout<<ans<<endl;
    return 0;
}