N = gets.to_i

dp = Array.new(101) { Array.new(26) { Array.new(7, 0) } }
dp[0][0][0] = 1.0

N.times do |i|
  0.upto(25) do |j|
    hit_rate = Rational(25 - j, 99 - i)
    miss_rate = 1.0 - hit_rate

    if j == 25
      0.upto(5) do |k|
        dp[i + 1][j][k] += dp[i][j][k]
      end
    else
      0.upto(5) do |k|
        r = Rational(5 - k, 25 - j)
        m = 1.0 - r

        dp[i + 1][j + 1][k + 1] += dp[i][j][k] * hit_rate * r
        dp[i + 1][j + 1][k] += dp[i][j][k] * hit_rate * m
        dp[i + 1][j][k] += dp[i][j][k] * miss_rate
      end
    end
  end
end

ans = (0..25).map { |x| dp[N][x][5] }.sum.to_f * 12

puts ans.round(12)