View Code of Problem 18

#include <iostream>
using namespace std;

int main()   
{//a[2]=1  a[3]=1 a[4]=2 a[5]=6
	int a[10000],n=0;
	a[0]=0;
	a[1]=0;
	a[2]=1;
	for(int i=3;i<10000;i++)
	{
		a[i]=a[i-1]+i-1;
	}
	while(scanf("%d",&n)!=EOF)
	{
		int sum=a[(n+1)/2]+a[n-(n+1)/2];
		cout<<sum<<endl;
	}
	

	return 0;
}