#include <algorithm>
#include <array>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <optional>
#include <queue>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

int main() {
    int32_t n, k;
    cin >> n >> k;
    vector<int32_t> as(n);
    for (auto &&a : as) {
        cin >> a;
    }
    int64_t sum = accumulate(as.begin(), as.end(), int64_t(0));
    reverse(as.begin(), as.end());
    int64_t ans = 0, kp = 1;
    for (auto a : as) {
        ans = ((a * kp) % sum + ans) % sum;
        kp = (kp * k) % sum;
    }
    cout << ans << endl;
    return 0;
}