otoczka-now working

#include <cstdio>
#include <functional>
#include <algorithm>
#include <math.h>
#include <queue>

using namespace std;

struct point {
    int x;
    int y;
};
point P1;

int iloczyn(point a, point b, point c) {
    int pole = (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
    if (pole > 0)
        return -1;
    else if (pole < 0)
        return 1;
    return 0;
}

int dist(point a, point b) {
    int dx = a.x - b.x, dy = a.y - b.y;
    return dx*dx + dy*dy;
}

bool comp(point a, point b){
    int order = iloczyn(a, b, P1);
    if (order == 0)
        return !(dist(P1, a) < dist(P1, b));
    return !(order == -1);
}

int main() {
    P1.x = 500000;
    P1.y = 500000;

    int n;      scanf("%d", &n);

    point *tab = new point[n-1];

    int x, y;       scanf("%d %d", &x, &y);      P1.x = x; P1.y = y;

    //////////////////////////////////////
    for (int i = 0; i < n-1; i++) {
        scanf("%d %d", &x, &y);
        tab[i].x = x; tab[i].y = y;
        if (tab[i].x < P1.x || (tab[i].x == P1.x && tab[i].y < P1.y)) {
            swap(P1, tab[i]);
        }
    }
    sort(tab, tab + n-1, comp);

    vector<point> otoczka;
    otoczka.push_back(tab[0]);
    otoczka.push_back(tab[1]);
    otoczka.push_back(tab[2]);
    for (int i = 3; i < n - 1; i++) {
        point top = otoczka.back();
        otoczka.pop_back();
        while (iloczyn(otoczka.back(), top, tab[i]) == -1) {
            top = otoczka.back();
            otoczka.pop_back();
        }
        otoczka.push_back(top);
        otoczka.push_back(tab[i]);
    }
    //////////////////////////////////////

    printf("%c", 'X');
    return 0;
}
//@author Tooster
/*
5
1 1
1 2
2 3
3 2
2 1

*/