View Code of Problem 18

#include<stdio.h>
#include<string.h>
int main(){
	int n,i;
	int f[10000];
	 while(scanf("%d",&n)!=EOF)
	 {
		 f[3]=1;
		 f[4]=2;
		 for (i=5;i<=n;i++)
		   f[i]=f[i-1]+i-3;
		 printf("%d\n",f[n]);
	 }	 
	return 0;
}