cf975d Ghosts

ref

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
using namespace std;
typedef long long ll;
typedef pair<int,int> pir;
int n, a, b, uu, vv, ww;
map<ll,int> mp1;
map<pir,int> mp2;
int main(){
    cin>>n>>a>>b;
    ll ans=0;
    for(int i=1; i<=n; i++){
        scanf("%d %d %d", &uu, &vv, &ww);
        ll tmp1 = (ll)a * vv - ww;
        pir tmp2=make_pair(vv, ww);
        ans += mp1[tmp1] - mp2[tmp2];
        mp1[tmp1]++;
        mp2[tmp2]++;
    }
    cout<<ans*2<<endl;
    return 0;
}