def powf(x,n):
    if n == 0:
        return 1
    k = 1
    while n>1:
        if n%2 != 0:
            k *= x
        x *= x
        n //= 2
    return k*x

n,k = map(int,input().split())
a = list(map(int,input().split()))
s = sum(a)
ans = 0
cnt = 1
for i in range(n):
    ans += a[n-1-i]*cnt
    cnt *= k
print(ans%s)