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#include <bits/stdc++.h>

using namespace std;

int n;

int first_type[3000000];
int second_type[3000000];
int M = 1500000;

int main(){
	cin.tie(0);
	cout.tie(0);
	ios_base::sync_with_stdio(false);

	cin >> n;

	for (int i = 0; i < n; ++i)
	{
		int r;
		cin >> r;
		if(r == 1){
			int w, t;
			cin >> w >> t;
			first_type[w - t + M]++;
		}
		else{
			int w, t;
			cin >> w >> t;
			second_type[w - t + M]++;
		}
	}

	long long ans = 0;
	for (int i = 0; i < 3000000; ++i)
	{
		ans += min(first_type[i], second_type[i]);
	}
	cout << ans << endl;
	return 0;
}