#include <bits/stdc++.h>
template<class T> inline bool chmin(T&a, T b){if(a > b){a = b; return true;}else{return false;}}
template<class T> inline bool chmax(T&a, T b){if(a < b){a = b; return true;}else{return false;}}
#define ll long long
#define double long double
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define mod (ll)(1e9+7)
#define inf (ll)(3e18+7)
#define eps (double)(1e-9)
#define pi (double) acos(-1)
#define P pair<int,int>
#define PiP pair<int,pair<int,int>>
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
using namespace std;

ll modpow(ll a, ll n, ll modo) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % modo;
        a = a * a % modo;
        n >>= 1;
    }
    return res;
}

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