View Code of Problem 18

#include <stdio.h>
#include <stdlib.h>
int main()
{
  int n;
  int i;
  int a[10000];
  a[0]=0;
  a[1]=0;
  a[2]=1;
  for(i=3;i<10000;i++)
  {
    a[i]=a[i-1]+i-1;//a[3]=3 a[4]=615.    
  }    while(scanf("%d",&n)!=EOF)
  {
    int sum;
    sum=a[(n+1)/2]+a[n-(n+1)/2];
    printf("%d\n",sum);
  }
  return 0;
}