Forest

input/code.cpp: In function 'int main()':
input/code.cpp:62:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
                   ^
input/code.cpp:65:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&X,&Y);
                        ^
input/code.cpp:69:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&x,&y);
                            ^

#include <cstdio>
#include <queue>
#include <algorithm>
#include <vector>
#include <set>
#include <cstdlib>

#define all(x) (x).begin(),x.end()

#define pb push_back
#define mp make_pair
#define x1 first
#define x2 second.first
#define x3 second.second
#define trip(a,b,c) mp(a,mp(b,c))

using namespace std;
const int inf = 1000000007;

int qrt(int x,int y)
{
    if(y >= 0)
    {
        if(x >= 0)
            return 0;
        else
            return 1;
    }
    else
    {
        if(x >= 0)
            return 3;
        else
            return 2;
    }
}


int cmp(const pair<int,int>& s1, const pair<int,int>& s2)
{

        int q1 = qrt(s1.first,s1.second);
        int q2 = qrt(s2.first,s2.second);
        if(q1 != q2)
            return q1 < q2;

        return ((long long)s1.first)*s2.second - ((long long)s1.second)*s2.first > 0;
                 }

struct less_than_key
{
        inline bool operator() (const pair<int,int>& s1, const pair<int,int>& s2)
        {
            return cmp(s1,s2);
        }
};


int main()
{
    int n;
    scanf("%d",&n);
    vector<pair<int,int> > inp(n);
    int X,Y;
    scanf("%d%d",&X,&Y);
    for(int i=0;i<n;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        x -= X;
        y -= Y;
        inp[i] = make_pair(x,y);
    }
    sort(all(inp),less_than_key());
    
    int ans = 1;
    for(int i=1;i<n;i++)
        if(cmp(inp[i-1],inp[i]))
            ans++;
    printf("%d\n",ans);

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED