from scipy import integrate

k = []

# 積分する関数の定義(今回はx^2)
def f(x):
    res = 0
    base = 1
    for c in k:
        res += c*base
        base *= x
    return res

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

for i in range(n):
    xd = int(input())
    k.append(xd)

ans,err = integrate.quad(f,a,b)

# 積分近似値の表示
print(int(ans))