View Code of Problem 18

#include<stdio.h>
#include<string.h> 
int main()
{
	int n,i;
	while(scanf("%d",&n)!=EOF)
	{
		if(n==3)
		{
			printf("1\n");
		}
		else if(n==1||n==2)
		{
			printf("0\n");
		}
		else{
		int sum=1;
		for(i=n-3;i>0;i--)
		{
			sum=sum+i;
		}
		printf("%d\n",sum);
		}
	}
}