import sys
input = sys.stdin.readline
def getlist(): return list(map(int, input().split()))
        
def main():
    n,k = getlist()
    a = getlist()
    total = sum(a)
    ans = 0
    K = 1
    for i in range(n-1,-1,-1):
        ans += a[i] * K
        K *= k
        K %= total
        ans %= total
    print(ans)

if __name__ == '__main__':
    main()