#include <bits/stdc++.h>
using namespace std;
template <typename T> using vec = vector<T>;
template <typename T> using vvec = vec<vec<T>>;
template <typename T> using lqueue = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using gqueue = priority_queue<T, vector<T>, less<T>>;

int main() {
    auto mpow = [](int64_t a, int64_t b, int64_t c) {
        int64_t ans = 1;
        while (b) {
            if (b & 1) {
                ans = (ans * a) % c;
            }
            a = (a * a) % c;
            b >>= 1;
        }
        return ans;
    };

    int n, k; cin >> n >> k;
    vec<int> a(n);
    for (auto &e : a) cin >> e;
    reverse(begin(a), end(a));

    int64_t ans = 0, mod = accumulate(begin(a), end(a), int64_t(0));
    for (int i = 0; i < n; ++i) {
        ans += a[i] * mpow(k, i, mod);
        ans %= mod;
    }

    cout << ans << endl;
}