from scipy.stats import norm 
from  math import sqrt
n=int(input())
l,r=map(int,input().split())

dp=[0 for i in range(6*n+1)]
dp[1:7]=[1 for i in range(6)]
if n<1000:
	for i in range(n-1):
		temp=[0 for i in range(6*n+1)]  
		for j in range(1,6*(i+1)+1):
			s=0
			for k in range(1,7):
				if j-k>0:
					s+=dp[j-k]
				temp[j]=s
		dp=temp

	a=sum([dp[i] for i in range(l,r+1)])
	print(a/6**n) 
else:
	l_=l-3.5*n/(sqrt(n*35/12))
	r_=r-3.5*n/(sqrt(n*35/12))
    
	print(norm.cdf(r_)-norm.cdf(l_))