codeforces 514B

题目：

B. Han Solo and Lazer Gun

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

There are n Imperial stormtroopers on the field. The battle field is a plane with Cartesian coordinate system. Each stormtrooper is associated with his coordinates (x, y) on this plane.

Han Solo has the newest duplex lazer gun to fight these stormtroopers. It is situated at the point (x0, y0). In one shot it can can destroy all the stormtroopers, situated on some line that crosses point (x0, y0).

Your task is to determine what minimum number of shots Han Solo needs to defeat all the stormtroopers.

The gun is the newest invention, it shoots very quickly and even after a very large number of shots the stormtroopers don't have enough time to realize what's happening and change their location.

Input

The first line contains three integers n, x0 и y0 (1 ≤ n ≤ 1000,  - 104 ≤ x0, y0 ≤ 104) — the number of stormtroopers on the battle field and the coordinates of your gun.

Next n lines contain two integers each xi, yi ( - 104 ≤ xi, yi ≤ 104) — the coordinates of the stormtroopers on the battlefield. It is guaranteed that no stormtrooper stands at the same point with the gun. Multiple stormtroopers can stand at the same point.

Output

Print a single integer — the minimum number of shots Han Solo needs to destroy all the stormtroopers.

Examples

input

4 0 01 12 22 0-1 -1

output

2

input

2 1 21 11 0

output

1

Note

Explanation to the first and second samples from the statement, respectively:

分析：

数据结构里面找到的题...然而并没想到数据结构解法？...

判有多少种不同的斜率 考虑到浮点数带来的误差，可用最简分数来描述斜率

代码：

#include<bits/stdc++.h>using namespace std;typedef pair<int,int> P;set<P> s;int gcd(int a,int b){//if(b>a) swap(a,b);//交换的话负数会出问题 if(b==0) return a;else return gcd(b,a%b);}int main(){ios_base::sync_with_stdio(false);int n,x,y;int a,b,ans=0;s.clear();cin>>n>>x>>y;while(n--){cin>>a>>b;a-=x,b-=y;int mod=gcd(a,b);a/=mod;b/=mod;P p=P(a,b);//cout<<p.first<<"  "<<p.second<<endl;if(!s.count(p)) ans++,s.insert(p);}cout<<ans<<endl;return 0;}