View Code of Problem 18

#include <stdio.h>
int main(){
	int n,i;
	while(scanf("%d",&n)!=EOF){
		int x=0;
		int y=0;
		int sum=0;
		if(n==0||n==1||n==2)
			printf("0\n");
			
		else if(n%2==1){
			x=(n+1)/2;
			y=(n-1)/2;
			for(i=1;i<x;i++){
				sum+=i;
			}
			for(i=1;i<y;i++){
				sum+=i;
			}
			printf("%d\n",sum);
		}
		else 
		{
			x=(n+1)/2;
			for(i=1;i<x;i++){
				sum+=i;
			}
			printf("%d\n",2*sum);
		}
			
    }
}