from scipy import integrate

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

def f(x):
    ret = 0
    for i in range(N+1):
        ret += K[i] * x**i
    return ret

ans,err = integrate.quad(f,A,B)

print(int(ans+err))