#include<stdio.h>

#define dim 1001

int main()
{
	freopen("patrate3.in","r",stdin);
	freopen("patrate3.out","w",stdout);

	float a[dim],b[dim],c,c1,d,d1;

	long n,i,j,k,l,nr=0,e,f;

	scanf("%ld", &n);

	for(i=1; i<=n; ++i)

		scanf("%f%f", &a[i], &b[i]);

	for(i=1; i<n; ++i)

		for(j=i+1; j<=n; ++j)
		{
			if(a[i]>a[j])

				d=a[i]-a[j];

			else

				d=a[j]-a[i];

			if(b[i]>b[j])

				c=b[i]-b[j];

			else

				c=b[j]-b[i];

			e=d*1000000;

			if(e%1000==998)

				d+=0.000002;

			for(k=i+1; k<=n; ++k)

				for(l=k+1; l<=n; ++l)
				{
					if(a[k]>a[l])

						d1=a[k]-a[l];

					else

						d1=a[l]-a[k];

					if(b[k]>b[l])

						c1=b[k]-b[l];

					else

						c1=b[l]-b[k];


					f=d1*1000000;

					if(f%1000==998)

						d1+=0.000002;


					if(d==d1 && c==c1)

						++nr;

				}
		}
	printf("%ld", nr);

	return 0;
}