from fractions import Fraction

n, A, B = map(int, input().split())
pA = 1
pB = 1
ans = Fraction(0)
for d in range(n + 1):
    K = int(input())
    pA *= A
    pB *= B
    ans += Fraction(K, d + 1) * (pB - pA)
print(ans.numerator // ans.denominator)