#include<bits/stdc++.h>
#define Gc() getchar()
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define eb emplace_back
#define all(x) x.begin(),x.end()
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;
const int N=1e5+5,M=N*4+5,K=1000+5,mod=998244353,Mod=mod-1;const db eps=1e-9;const int INF=1e9+7;mt19937 rnd(28382);
#define Tp template<typename T>
#define Ts template<typename T,typename... Ar>
namespace Debug{
	Tp void _debug(char* f,T t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,T x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	#ifdef LOCAL
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
	#else 
	#define gdb(...) void()
	#endif
}using namespace Debug;
int n,A[N],B[N];
void Solve(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++) scanf("%d%d",&A[i],&B[i]);
	ll g=0,sx=A[2]-A[1],sy=B[2]-B[1];
	if(sx<0) sx*=-1,sy*=-1;
	for(int i=3;i<=n;i++){
		ll tx=A[i]-A[1],ty=B[i]-B[1];
		if(tx<0) tx*=-1,ty*=-1;
		while(tx){
			ll w=sx/tx;
			sx-=tx*w;sy-=ty*w;
			swap(sx,tx);swap(sy,ty);
		}
		g=__gcd(g,abs(ty));
	}
	if(!g){puts("-1");return;}
	printf("%lld\n",g*sx);
}
int main(){
	int t=1;
	// scanf("%d",&t);
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}