#include<bits/stdc++.h>
using namespace std;
#pragma region atcoder
//#include <atcoder/modint>
//using namespace atcoder;
//using mint = modint998244353;
//using mint = modint1000000007;
#pragma endregion
#pragma region debug for var, v, vv
#define debug(var)  do{std::cerr << #var << " : ";view(var);}while(0)
template<typename T> void view(T e){std::cerr << e << std::endl;}
template<typename T> void view(const std::vector<T>& v){for(const auto& e : v){ std::cerr << e << " "; } std::cerr << std::endl;}
template<typename T> void view(const std::vector<std::vector<T> >& vv){cerr << endl;int cnt = 0;for(const auto& v : vv){cerr << cnt << "th : "; view(v); cnt++;} cerr << endl;}
#pragma endregion
using ll = long long;
const ll mod = 1000000007;
const int inf = 1001001001;
const ll INF = 1001001001001001001ll; 
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
template<class T, class K>bool chmax(T &a, const K b) { if (a<b) { a=b; return 1; } return 0; }
template<class T, class K>bool chmin(T &a, const K b) { if (b<a) { a=b; return 1; } return 0; }
ll rudiv(ll a, ll b) { return a/b+((a^b)>0&&a%b); } //  20 / 3 == 7
ll rddiv(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // -20 / 3 == -7
ll power(ll a, ll p){ll ret = 1; while(p){if(p & 1){ret = ret * a;} a = a * a; p >>= 1;} return ret;}
ll modpow(ll a, ll p, ll m){ll ret = 1; while(p){if(p & 1){ret = ret * a % m;} a = a * a % m; p >>= 1;} return ret;}
/*---------------------------------------------------------------------------------------------------------------------------------*/
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    //cout << fixed << setprecision(20);
    ll n, k; cin >> n >> k;
    vector<ll> a(n);
    for(int i = 0; i < n; i++) cin >> a[i];
    ll m = accumulate(a.begin(), a.end(), 0ll);
    ll cnt = 1, ans = 0;
    for(int i = n - 1; i >= 0; i--){
        ans += cnt * a[i] % m;
        if(ans >= m) ans -= m;
        cnt = cnt * k % m;
    }
    cout << ans << endl;
}       
/*
   * review you code when you get WA (typo? index?)
   * int overflow, array bounds
   * special cases (n=1?)
*/