#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define ppb pop_back
#define ep insert
#define endl '\n'
#define elif else if
#define pow pwr
#define sqrt sqrtt
#define int long long
#define ll long long
#define y1 YONE
typedef unsigned long long ull;
using namespace std;
const int N=1e5+5;
int x[N],y[N],n;
int32_t main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
cin>>n;
for (int i=1;i<=n;i++) cin>>x[i]>>y[i];
if (n<=2){
cout<<-1<<endl;
return 0;
}
if (x[1]==x[2] && x[1]==x[3]){
cout<<-1<<endl;
return 0;
}
if (y[1]==y[2] && y[1]==y[3]){
cout<<-1<<endl;
return 0;
}
if (x[1]!=x[2] && x[1]!=x[3] && x[2]!=x[3] && y[1]!=y[2] && y[1]!=y[3] && y[2]!=y[3]){
cout<<-1<<endl;
return 0;
}
sort(x+1,x+1+n);
sort(y+1,y+1+n);
int X=x[3]-x[1]+1,Y=y[3]-y[1]+1;
cout<<X*Y-X-Y+1<<endl;
return 0;
}
