View Code of Problem 18

#include <stdio.h>
#include <string.h>
#include <math.h>
int main(){
  int n,k=0,i,a[10000]={0};
    for(i=1;i<10000;i++){
      a[i]=a[i-1]+k;
      if(i%2==0) 
        k++;
    }
  
  while(~scanf("%d",&n)){
    printf("%d\n",a[n]);
    
  }


}