N,K=map(int,input().split())
A=list(map(int,input().split()))

A=A[::-1]

mod=sum(A)

L=[1]
for i in range(1,N):
    L.append(L[-1]*K%mod)
#print(L)

ans=0
for i in range(N):
    ans+=A[i]*L[i]
print(ans%mod)