#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define all(s) (s).begin(),(s).end()
#define vcin(n) for(ll i=0;i<ll(n.size());i++) cin>>n[i]
#define rever(vec) reverse(vec.begin(), vec.end())
#define sor(vec) sort(vec.begin(), vec.end())
#define fi first
#define se second
const ll mod = 998244353;
//const ll mod = 1000000007;
const ll inf = 2000000000000000000ll;
static const long double pi = 3.141592653589793;
template<class T,class U> void chmax(T& t,const U& u){if(t<u) t=u;}
template<class T,class U> void chmin(T& t,const U& u){if(t>u) t=u;}
ll modPow(ll a, ll n, ll mod) { ll ret = 1; ll p = a % mod; while (n) { if (n & 1) ret = ret * p % mod; p = p * p % mod; n >>= 1; } return ret; }

int main() {
  /* mod は 1e9+7 */
  ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
  cout<< fixed << setprecision(10);
  ll n,k;
  cin>>n>>k;
  vector<ll> a(n);
  vcin(a);
  ll tmp=0;
  for(int i=0;i<n;i++){
    tmp+=a[i];
  }
  ll ans=0;
  ll ki=1;
  for(int i=n-1;i>=0;i--){
    ans+=a[i]*ki;
    ans%=tmp;
    ki*=k;
    ki%=tmp;
  }
  cout<<ans<<endl;
}