maxn = 505
db = float

def solve():
    n, a, b = map(int, input().split())
    vec = list(map(int, input().split()))

    dp = [[0.0] * (maxn) for _ in range(maxn)]
    ndp = [[0.0] * (maxn) for _ in range(maxn)]

    dp[0][0] = 1.0

    for i in range(1, n+1):
        for x in range(i+1):
            for y in range(b+1):
                ndp[x][y] += dp[x][y]
                if y + vec[i-1] <= b:
                    ndp[x+1][y + vec[i-1]] += dp[x][y] * (x+1) / (n-x)
        for x in range(maxn):
            dp[x] = ndp[x][:]

    ans = 0.0
    for i in range(1, n+1):
        ndp = [row[:] for row in dp]
        for x in range(n):
            for y in range(b+1):
                ndp[x+1][y+vec[i-1]] -= ndp[x][y] * (x+1) / (n-x)
        temp = 0.0
        for x in range(n-1):
            for y in range(a, b+1):
                if y + vec[i-1] > a and y + vec[i-1] <= b:
                    temp += ndp[x][y] / (n-x)
        ans += temp

    print('{:.50f}'.format(ans))

solve()