n,a,b=map(int,input().split())

f=0
c=11*9*8*7*5

for i in range(n+1):
    k=int(input())
    s=b**(i+1)*k*c//(i+1)
    t=a**(i+1)*k*c//(i+1)
    f=f+s-t
    
print(f//c)