#include <bits/stdc++.h>

struct Vector {
    int64_t x, y;

    Vector() : x(0), y(0) { ; }
    Vector(int64_t x, int64_t y) : x(x), y(y) { ; }

    int64_t operator%(const Vector& other) const {
        return int64_t(x) * other.y - int64_t(y) * other.x;
    }
};

int32_t main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int n;
    std::cin >> n;
    std::vector<Vector> input(n);
    for (auto& [x, y] : input) {
        std::cin >> x >> y;
    }
    if (n == 1) {
        std::cout << "-1\n";
        return 0;
    }
    if (n == 2) {
        if (input[0] % input[1]) {
            std::cout << llabs(input[0] % input[1]) << std::endl;
        } else {
            std::cout << "-1\n";
        }
        return 0;
    }

    return 0;
}