#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N, K;
	cin >> N >> K;
	vector<int> A( N );
	for( int i = 0; i < N; i++ ) cin >> A[i];

	long long s = 0;
	long long a = 0;
	long long k = 1;
	for( int i = N - 1; i >= 0; i-- ) {
		s += A[i];
		a += A[i] * k;
		k *= K;
	}
	long long ans = a % s;

	cout << ans << endl;
}