#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
long long a[100010];
int main() {
    long long n, k;
    cin >> n >> k;
    long long sum = 0;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        sum += a[i];
    }
    long long ans = 0;
    long long now = 1;
    for (int i = n - 1; i >= 0; i--) {
        ans += now * a[i] % sum;
        ans %= sum;
        now *= k;
        now %= sum;
    }
    cout << ans << endl;
}