Forest

#include <iostream>
#include <set>
#include <algorithm>

using namespace std;

int gcd(int a,int b){
    if (b== 0) return a;
    return gcd(b, a % b);
}
int main()
{
	cin.sync_with_stdio(false);	
	
    int n,ux,uy;
    cin>>n>>ux>>uy;
    
    set<pair<int,int>> t;
    
    int tx,ty,dx,dy,g;
    for (int i=0;i<n;i++){
        cin>>tx>>ty;
        dx=tx-ux;
        dy=ty-uy;
        
        g=gcd(abs(dx),abs(dy));
        t.insert(make_pair(dx / g, dy / g));
    }
    
    cout<<t.size()<<endl;

	return 0;
}

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