from fractions import Fraction

N,A,B = map(int,input().split())
ans = 0
for i in range(N+1):
  K = int(input())
  p = Fraction(K * (B ** (i+1) - A ** (i+1))) / Fraction(i+1)
  ans += p
Trueans = ans.numerator // ans.denominator
print(Trueans)