def main():
    n, a, b = map(int, input().split())
    f = 1
    for i in range(n+1):
        f *= i+1
    ans = 0
    for i in range(n+1):
        k = int(input())
        ans += k*(b**(i+1)-a**(i+1))*f//(i+1)
    print(ans//f)


if __name__ == "__main__":
    main()