#include<bits/stdc++.h>
using std::cin, std::cout;
int n, m;
using pr = std::pair<int, int>;
const int N = 10005;
std::vector<pr> dp[N];
int rank[N][3];
int get(int x, int y, int z) {
	if(x >= y && x >= z) return 0;
	if(y > x && y >= z) return 1;
	return 2;
}
int per[3];
int min(int x, int y) { return per[x] < per[y] ? x : y; }
int main() {
	std::ios::sync_with_stdio(false), cin.tie(0);
	cin >> n;
	for(int i = 1;i <= n;++i) {
		for(int j = 0;j < 3;++j) {
			cin >> rank[i][j];
			-- rank[i][j];
		}
	}
	for(int i = 0;i <= n;++i) {
		dp[i].emplace_back(get(i, 0, n - i), 0);
		for(int j = 1;j + i <= n;++j) {
			int w = get(i, j, n - i - j);
			if(w != dp[i].back().first) {
				dp[i].emplace_back(w, j);
			}
		}
		dp[i].emplace_back(0, n + 1);
	}
	for(int i = n;i >= 1;--i) {
		for(int j = 0;j < 3;++j) per[rank[i][j]] = j;
		for(int j = 0;j < i;++j) {
			static std::vector<pr> res; res.clear();
			auto & A = dp[j];
			auto & B = dp[j + 1];
			for(int i = 1;i + 1 < (int) A.size();++i) {
				if(per[A[i].first] < per[A[i - 1].first]) {
					-- A[i].second;
				}
			}
			int id = 0;
			int x = 0, y = 0;
			for(;id < i;) {
				for(;A[x + 1].second <= id;) x += 1;
				for(;B[y + 1].second <= id;) y += 1;
				int w = min(A[x].first, B[y].first);
				if(!id || w != res.back().first) {
					res.emplace_back(w, id);
				}
				id = std::min(A[x + 1].second, B[y + 1].second);
			}
			res.emplace_back(0, i);
			dp[j] = res;
		}
	}
	cout << dp[0][0].first + 1 << '\n';
}