def main():
   
   K = int(input())
   
   dp = [0] * (K+10)
   for i in range(K-1, -1, -1):
   	  for j in range(1, 7):
   	  	  dp[i] += dp[i+j] / 6
   	  dp[i] += 1
   print(dp[0])
   
   
if __name__ == '__main__':
    main()