K = int(input())
DP = [0]*(K+2)

def dfs(wa,kitai):
    if wa>=K:
        return 0
    if DP[wa]:
        return DP[wa]
    temp = 0
    temp += (dfs(wa+1,kitai+1)+1)/6
    temp += (dfs(wa+2,kitai+1)+1)/6
    temp += (dfs(wa+3,kitai+1)+1)/6
    temp += (dfs(wa+4,kitai+1)+1)/6
    temp += (dfs(wa+5,kitai+1)+1)/6
    temp += (dfs(wa+6,kitai+1)+1)/6
    DP[wa] = temp
    return DP[wa]
dfs(0,0)
print(DP[0])