View Code of Problem 18

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