from fractions import Fraction
N,A,B = list(map(int,input().split()))
K = [int(input()) for _ in range(N+1)]

ans = 0
for i in range(N+1):
    ans += Fraction(K[i] * pow(B,i+1),i+1) - Fraction(K[i] * pow(A,i+1),i+1)
a,b = ans.as_integer_ratio()
print(a//b)