#include <iostream>
#include <vector>

using lint = long long;

int main(){
	lint n, k;
	std::cin >> n >> k;
	std::vector<lint> a(n);
	lint sum = 0;
	for(lint &i : a){
		std::cin >> i;
		sum += i;
	}
	lint tmp = 1;
	lint ans = 0;
	for(auto it = a.rbegin(); it != a.rend(); ++it){
		ans = (ans + *it * tmp) % sum;
		tmp = tmp * k % sum;
	}
	std::cout << ans << std::endl;
}