//
// Created by zeronosu77108 on Jan 15, 2021.
//
#include <iostream>
#include <iomanip>
#include <vector>
#include <utility>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <queue>
#include <cmath>
#include <numeric>
#include <set>
#include <complex>
#include <optional>

using namespace std;
struct aaa{aaa(){cin.tie(nullptr); ios::sync_with_stdio(false); cout<<fixed<<setprecision(20);};}aaa;
template <class T>ostream &operator<<(ostream &o,const vector<T>&v){o<<"{";for(int i=0;i<(int)v.size();i++)o<<(i>0?", ":"")<<v[i];o<<"}";return o;}
#define debug(v) {cerr<<"\033[1;36m[debug]\033[m "<<#v<<" : "<<(v)<<endl;}

using int64 = long long;

int main() {
    int n, k;
    string s;
    cin >> n >> k;

    vector a(n, 0L);
    for (int i=0; i<n; i++) cin >> a[i];
    long sum = accumulate(a.begin(), a.end(), 0L);

    long ans = 0;
    for (long i=n-1, d=1; i>=0; i--) {
        ans += d * a[i];
        ans %= sum;
        d *= k;
        d %= sum;
    }

    cout << ans << endl;
}