#include<bits/stdc++.h>
#define poly vector<int>
#define IOS ios::sync_with_stdio(false)
#define ll long long
#define mp make_pair
#define mt make_tuple
#define pa pair < int,int >
#define fi first
#define se second
#define inf 1e18
#define mod 998244353
#define sz(x) ((int)((x).size()))
#define int ll
#define N 2005
using namespace std;
class point{
 	public:
	double x;
	double y;
	point(double x_=0,double y_=0):x(x_),y(y_){} 
	friend const bool operator<(const point& p1,const point& p2){
		return (p1.x==p2.x)?p1.y<p2.y:p1.y<p2.y;
	};
	friend const point operator+(const point& p1,const point& p2){
		return point(p1.x+p2.x,p1.y+p2.y);
	};
	friend const point operator-(const point& p1,const point& p2){
		return point(p1.x-p2.x,p1.y-p2.y);
	};
	friend const point operator*(const point& p,const double& m){
		return point(p.x*m,p.y*m);
	};
	friend const point operator*(const double& m,const point& p){
		return point(p.x*m,p.y*m);
	};
	friend const point operator/(const point& p,const double& m){
		return point(p.x/m,p.y/m);
	};
	friend ostream& operator <<(ostream& out,point& a){
		printf("(%lf,%lf)",a.x,a.y);
		return out;
	};
};
int n,dfn[N],DFN;
point a[N];
typedef point vect2;
 
class line{
	public:
	point start;
	point end; 
	line(point s=point(0,0),point e=point(0,0)):start(s),end(e){}
};
double dot(point x,point y)
{
    return x.x*y.x+x.y*y.y;
}
point projection(point p,point a,point b)
{
    point v = b - a,u = p - a;
    return a + v * (dot(v,u) / dot(v,v));	//dot是两向量的点积
}
void BellaKira()
{
    cin>>n;
    for (int i=1;i<=n;i++)
        cin>>a[i].x>>a[i].y,a[i].x*=2,a[i].y*=2;
    if (n<=2)
    {
        cout<<"-1\n";
        return;
    }
    //check (0,0)
    {
        map<pa,int>Mp;
        bool ans=1;
        for (int i=1;i<=n;i++)
        {
            if (a[i].x==0&&a[i].y==0) continue;
            if (Mp.count(mp(-a[i].x,-a[i].y))) Mp.erase(mp(-a[i].x,-a[i].y));
            else Mp[mp(a[i].x,a[i].y)]=1;
        }
        if (Mp.empty())
        {
            cout<<"-1\n";
            return;
        }
    }
    int ans=n;
    for (int i=1;i<=n;i++)
    {
        map<double,int>Mp;
        for (int j=1;j<=n;j++)
            if (j!=i) 
            {
                point now=a[j]-a[i];
                Mp[now.y/now.x]++;
            }
        ans=min(ans,(int)Mp.size()+1);
    }
    cout<<ans<<'\n';
}
signed main()
{
    IOS;
    cin.tie(0);
    int T=1;
    while (T--)
    {
        BellaKira();
    }
}