#include <bits/stdc++.h>   using namespace std;   struct Point {     int x;     int y;   };   int main() {     int n;     cin >> n;     Point P[n];     for (int i = 0; i < n; i++) {       cin >> P[i].x >> P[i].y;     }     int val;     if (n < 2)       val = -1;     else if (n == 2) {       if (P[0].x != P[1].x && P[0].y != P[1].y)         val = abs(P[0].x - P[1].x) * abs(P[0].y - P[1].y);       else         val = -1;     } else {       int alt, larg;       if ((P[0].x - P[1].x) != 0)         alt = P[0].x - P[1].x;       else {         alt = P[0].x - P[2].x;       }       if ((P[0].y - P[1].y) != 0)         larg = P[0].y - P[1].y;       else {         larg = P[0].y - P[2].y;       }       val = abs(alt * larg);     }     cout << val << endl;   }   