CF457D.Bingo!

普及/提高-

通过率:0%

AC君温馨提醒

该题目为【codeforces】题库的题目,您提交的代码将被提交至codeforces进行远程评测,并由ACGO抓取测评结果后进行展示。由于远程测评的测评机由其他平台提供,我们无法保证该服务的稳定性,若提交后无反应,请等待一段时间后再进行重试。

题目描述

The game of bingo is played on a 5×55×5 square grid filled with distinct numbers between 11 and 7575 . In this problem you will consider a generalized version played on an n×nn×n grid with distinct numbers between 11 and mm (m>=n2)(m>=n^{2}) .

A player begins by selecting a randomly generated bingo grid (generated uniformly among all available grids). Then kk distinct numbers between 11 and mm will be called at random (called uniformly among all available sets of kk numbers). For each called number that appears on the grid, the player marks that cell. The score at the end is 2 raised to the power of (number of completely marked rows plus number of completely marked columns).

Determine the expected value of the score. The expected score may be very large. If the expected score is larger than 109910^{99} , print 109910^{99} instead (for example as "1e99" without the quotes).

输入格式

Input will consist of three integers nn , mm , kk (1<=n<=300; n2<=m<=100000; n<=k<=m)(1<=n<=300; n^{2}<=m<=100000; n<=k<=m) .

输出格式

Print the smaller of 109910^{99} and the expected score. Your answer must be correct within an absolute or relative error of 10910^{-9} .

输入输出样例

  • 输入#1

    1 2 1
    

    输出#1

    2.5
    
  • 输入#2

    2 4 3
    

    输出#2

    4
    
  • 输入#3

    7 59164 40872
    

    输出#3

    3.1415926538
    
首页