View Code of Problem 18

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