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#include <stdio.h>
#include <time.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <map> 
#include <string>
#include <vector>  
#include <iostream> 
#include <sstream> 
#include <queue>
#include <algorithm>
#include <assert.h>


using namespace std;

#define ll long long
#define PB 		push_back
#define FOR(a,start,end) 	for(int a=int(start); a<int(end); a++)
#define INF 		INT_MAX
#define SORT(a) 	sort(a.begin(),a.end()) 
#define CL(a,x) 		memset(a,x,sizeof(a))
#define REP(a,x)	for(int a=0;a<x;a++)
#define REP1(a,x)	for(int a=1;a<=x;a++)
#define MP 		make_pair



typedef vector<ll>     vi;
typedef pair<ll, ll>     pii;
typedef vector<string> vs;
typedef vector<pii> vii;
typedef vector<vector<ll> > vvi;
typedef vector<vector<string> > vvs;
typedef vector<pair<string, string> > vss;
typedef pair<string, string> pss;
typedef pair<ll, pii> ppii;
typedef vector<ppii> vppii;
typedef vector<vector<pii> > vvii;
typedef vector<vvi> vvvi;


ll n, k, a, b, z;
vi vk, va1,va2;
vvi vva;

int main() {
	//	freopen("c:\\wojtek\\uva\\pa\\debug\\ele167.in", "rt", stdin);

	cin >> n;
	vk.assign(2000010, 0ll);
	vva.assign(2, vk);

	for (int i = 1; i <= n; i++) {
		cin >> a >> b >> k;
		vva[a - 1][b - k + 1000000]++;
	}
	z = 0;
	for (int i = 0; i <= 2000000; i++) {
		z += min(vva[0][i], vva[1][i]);

	}

	cout << z << endl;
	return 0;

}