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#include <bits/stdc++.h>
using namespace std;
typedef long long lld;
typedef double lf;
typedef long double llf;
typedef pair<int,int> pii;
typedef pair<lld,lld> pll;
#define For(i,s,a) for(int i = (int)s; i < (int)a; ++i)
#define rpt(s, it) for(auto it = s.begin(); it != s.end(); ++it)
#define brpt(s, it) for(auto it = s.rend(); it != s.rbegin(); --it)
#define sz size()
#define pb push_back
#define eb emplace_back
#define ff first
#define dd second
#define mp make_pair
#define all(x) (x).begin (x).end()
#define ZAPS {int t; scanf("%i", &t); while(t--) solve();}


template<typename Ta, typename Tb>
ostream & operator <<(ostream & os, pair<Ta, Tb> x){
	return os << x.ff << " " << x.dd;
}

int ile[2000001][2];

int32_t main(void){
	int n;
	scanf("%d", &n);
	For(i, 0, n){
		int k, w, t;
		scanf("%d%d%d", &k, &w, &t);
		--k;
		w += 1e6 - t;
		++ile[w][k];
	}
	int wyn = 0;
	For(i, 0, 2000001)
		wyn += min(ile[i][0], ile[i][1]);
	printf("%d", wyn);
}

/*
4
1 5 2
2 3 0
2 3 6
1 7 4
*/