#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
from scipy.stats import norm
import numpy as np

N, L, R = map(int, read().split())


def solve_small(N, L, R):
    if L > 6 * N:
        return 0
    R = min(R, 6 * N)
    dice = np.array([0, 1, 1, 1, 1, 1, 1], np.float64) / 6
    dp = np.ones(1)
    for _ in range(N):
        dp = np.convolve(dp, dice)
    return dp[L: R + 1].sum()


def solve_large(N, L, R):
    mu = 3.5 * N
    sigma = np.sqrt(35 * N / 12)
    ZR = (R + 0.5 - mu) / sigma
    ZL = (L - 0.5 - mu) / sigma
    return norm.cdf(ZR) - norm.cdf(ZL)


f = solve_small if N <= 5000 else solve_large
print(f(N, L, R))