#include <cstdio>
#include <iostream>
using namespace std;
int n,ans;
int x[100001],y[100001];
bool find(int a,int b)
{
	for(int i=1;i<=n;i++)
		if(x[i]==a&&y[i]==b)
			return true;
	return false;
}
int main()
{
	while(true)
	{
		scanf("%d", &n);
		ans=0;
		if(n==0) break;
		for(int i=1;i<=n;i++)
			scanf("%d%d",&x[i],&y[i]);
		for(int i=1;i<n;i++)
			for(int j=i+1;j<=n;j++)
			{
            	int midx=(x[i]+x[j])/2;
	            int midy=(y[i]+y[j])/2;            
    	        int x1=midx-(midy-y[i]),y1=midy+(midx-x[i]);
        	    int x2=midx+(midy-y[i]),y2=midy-(midx-x[i]);
        	    if(find(x1,y1)&&find(x2,y2) ans++;
        	}
		printf("%d\n", ans/2);
    }
	return 0;
}