hdu6195 cable cable cable

cable cable cable

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 2084    Accepted Submission(s): 1348

Problem Description

Connecting the display screen and signal sources which produce different color signals by cables, then the display screen can show the color of the signal source.Notice that every signal source can only send signals to one display screen each time. 

Now you have M display
screens and K different
signal sources(K≤M≤232−1).
Select K display
screens from M display
screens, how many cables are needed at least so that **any** K display
screens you select can show exactly K different
colors.

 

Input

Multiple cases (no more than 100),
for each test case:

there is one line contains two integers M and K.

 

Output

Output the minimum number of cables N.

 

Sample Input

3 2
20 15

 

Sample Output

4
90

Hint

As the picture is shown, when you select M1 and M2, M1 show the color of K1, and M2 show the color of K2.

When you select M3 and M2, M2 show the color of K1 and M3 show the color of K2.

When you select M1 and M3, M1 show the color of K1.

 

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题意：给出m个显示屏和k个信号，要求任选k个显示屏都可以显示所有的信号

思路：找规律

#include <iostream>

using namespace std;
typedef long long ll;
int main()
{
   ll m,k;
   while(cin>>m>>k)
   {

   ll tmp=m-(k+1);
   cout<<k*2+tmp*k<<endl;
   }
    return 0;
}