#include<bits/stdc++.h>
#define int long long
#define reg register
inline int read(){
	int k=1,x=0;char ch=getchar();
	while (ch<'0'||ch>'9') {if (ch=='-') k=-1; ch=getchar();}
	while (ch>='0'&&ch<='9') x=(x<<3)+(x<<1)+ch-48,ch=getchar();
	return k*x;
}
const int N=5e5+10,INF=1e18;
const long double K=sqrtl(3)/2;
int n;
struct Node{
	int x,y;
	inline Node operator-(const Node &A)const{return {x-A.x,y-A.y};}
	inline Node operator*(const int &A){return {A*x,A*y};}
	inline int operator*(const Node &A)const{return x*A.x+y*A.y;;}
	inline int operator^(const Node &A)const{return x*A.y-y*A.x;}
	inline int abs(){return x*x+y*y;}
}A,B,C,O;
inline int cabs(reg int x){return x<0?-x:x;}
inline Node gcd(reg Node p1,reg Node p2){
	reg int x=std::__gcd(cabs(p1.x),cabs(p2.x)),y=std::__gcd(p1.y,p2.y);
	return {x,y};
}
inline long double theta(reg Node p1,reg Node p2){
	reg int dot=cabs(p1*p2);
	return 1.0L*dot/sqrtl(p1.abs())/sqrtl(p2.abs());
}
inline void trans(reg Node &A,reg Node &B){
	if (A.abs()<B.abs()) std::swap(A,B);
	reg int k=roundl(1.0L*(A*B)/sqrtl(B.abs()));
	A=A-B*k;
}
signed main(){
	n=read(); if (n<=2) return puts("-1"),0;
	O.x=read(),O.y=read();
	for (reg int i=1;i<n;i++){
		C.x=read(),C.y=read(),C=C-O;
		if (C.y<0) C.x=-C.x,C.y=-C.y;
		if (!A.abs()) A=C; else if (A*C==0) A=gcd(A,C); 
		else if (!B.abs()) B=C; else if (B*C==0) B=gcd(B,C);
		else{
			while (A.abs()&&B.abs()&&C.abs()){
				if (theta(A,B)<K) trans(A,B);
				if (theta(C,B)<K) trans(C,B);
				if (theta(A,C)<K) trans(A,C); 
			}
			if (!A.abs()) A=C; 
			if (!B.abs()) B=C; 
		}
	}
	reg int ans=cabs(A^B); printf("%lld\n",ans?ans:-1);
	return 0;
}