import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

"""
F(x) = k[0]x^1 + k[1]x^2/2 + ... k[n]/(n + 1)x^{n+1}
F(A) - F(B)


"""
def f(X):
    res = 0
    for i in range(n + 1):
        res += Fraction(k[i]) * Fraction(X) ** (i + 1) / Fraction(i + 1)
    return res

from fractions import Fraction
n, a, b = na()
k = [ni() for i in range(n + 1)]

ans = f(b) - f(a)

print(ans._numerator//ans._denominator)