Getting RE in Psertu in Byteland

Here is the problem which I am solving https://www.codechef.com/problems/ECJAN20I
Following is my code:

#include <bits/stdc++.h>
using namespace std;

#define FASTIO ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);

struct point
{
    int x, y;
};

point p0;

int dist_sq(point p)
{
    return (p.x-p0.x)*(p.x-p0.x) + (p.y-p0.y)*(p.y-p0.y);
}

bool cmp(point p, point q)
{
    int val = (p.y-p0.y)*(q.x-p0.x) - (q.y-p0.y)*(p.x-p0.x);
    if(val == 0) return dist_sq(p) < dist_sq(q);
    else return (val < 0);
}

int orientation(point p, point q, point r)
{
    int val = (q.x-p.x)*(r.y-p.y) - (q.y-p.y)*(r.x-p.x);
    if(val == 0) return 0; //collinear
    else return (val < 0) ? 1 : 2; //1->cw and 2->ccw
}

int nextToTop(stack<int>& S)
{
    int p = S.top();
    S.pop();
    int q = S.top();
    S.push(p);

    return q;
}

int convexHull(vector<point>& arr)
{
    int n = arr.size();
    int l = 0;
    for(int i=0; i<n; i++)
    {
        if((arr[i].y < arr[l].y)||(arr[i].y == arr[l].y && arr[i].x < arr[l].x))
            l = i;
    }
    p0 = arr[l];
    sort(arr.begin(), arr.end(), cmp);

    stack<int> v;
    v.push(0);
    v.push(1);

    for(int i=2; i<n; i++)
    {
        while(v.size() != 1 && orientation(arr[nextToTop(v)],arr[v.top()],arr[i]) != 2)
            v.pop();
        v.push(i);
    }

    int cnt = 0;
    while(!v.empty())
    {
        v.pop();
        cnt++;
    }

    return cnt;
}

int main()
{
    FASTIO

    int t;
    cin >> t;
    while(t--)
    {
        int n, r;
        cin >> n >> r;
        vector<point> arr(n);

        for(int i=0; i<n; i++)
            cin >> arr[i].x >> arr[i].y;

        bool res = (convexHull(arr) <= r);

        if(res) cout << "YES\n";
        else cout << "NO\n";
    }

    return 0;
}

I have tried my code for the sample test case provided with the problem, along with some other test cases that I came up with. But on submitting my code I keep getting Runtime Error (SIGSEGV), and even SIGABRT sometimes. Can anyone please help me in resolving this issue?

@everule1 Please Help.