#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define chmin(x,y) x = min((x),(y));
#define chmax(x,y) x = max((x),(y));
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
const int INF = 1e9;
const long long LINF = 1e17;
const int MOD = 1000000007;
//const int MOD = 998244353;
const double PI = 3.14159265358979323846;

ll modpow(ll x,ll n,ll mod){
    ll ret = 1;
    while(n>0){
        if(n&1) ret = (ret * x) % mod;
        x = (x * x) % mod;
        n >>= 1;
    }
    return ret;
}

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