n = gets.to_i

def fact(n)
    (1..n).reduce{|s,e|s*e}
end

def combi(n, r)
    q = 1
    1.upto(r){|k|q=q*(n-k+1)/k}
    return q
end
def perm(n, r=1)
    q = 1
    n.downto(r+1){|nn|q*=nn}
    return q
end

if n < 6
    p 0;exit
end

if n > 100
    p 1;exit
end



dp = Array.new(6){0.to_r}
dp[0] = 1.to_r
(n-1).times{
    4.downto(0){|i|
        dp[i+1] += dp[i]*Rational(5-i, 6)
        dp[i] *= Rational(i+1,6)
    }
}
p dp[5].to_f