#pragma GCC optimize("Ofast,unroll-loops")

#include <bits/stdc++.h>

using namespace std;


using ll = long long;

#define flt double
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define rep(i, n) for(int i = 0; i < n; i += 1)
#define len(a) ((int)(a).size())


const ll inf = 1e18;
mt19937 rnd(234);


const int maxn = 1e4;
int n;
int p[maxn][3], pos[maxn][3];


int32_t main() {
    if (1) {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout.tie(0);
    }
    cin >> n;
    rep(i, n) {
        rep(j, 3) {
            cin >> p[i][j];
            --p[i][j];
        }
    }
    rep(i, n) {
        rep(j, 3) {
            pos[i][p[i][j]] = j;
        }
    }
    const int super_len = 9;
    vector<array<pair<int, int>, super_len>> dp(n + 1);
    for (int x = 0; x <= n; x += 1) {
        int i = 0;
        if (n - 2 * x > 0) {
            dp[x][i++] = make_pair(0, 2);
        }
        if (max(0, n - 2 * x) <= x) {
            dp[x][i++] = make_pair(max(0, n - 2 * x), 0);
        }
        int val = max({ x + 1, (n - x + 1) / 2 });
        if (val <= n - x) {
            dp[x][i++] = make_pair(val, 1);
        }
        for (; i < super_len; i += 1) {
            dp[x][i] = make_pair(10 * n + 10000, -1);
        }
    }
    for (int cnt = n - 1; cnt >= 0; cnt -= 1) {
        vector<array<pair<int, int>, 9>> ndp(cnt + 1);
        for (int x = 0; x <= cnt; x += 1) {
            auto& a = dp[x + 1];
            auto& b = dp[x];
            auto c = dp[x];
            for (auto& f : c) f.first -= 1;
            c[0].first = max(c[0].first, 0);
            int i = 0, j = 0, k = 0;
            if (c[0].first == c[1].first) k += 1;
            int last_min = -1;
            int cur_pos = 0;
            int vala = -1, valb = -1, valc = -1;
            int biba = 0;
            while (a[i].second <= n or b[j].second <= n or c[k].second <= n) {
                cur_pos = min({ a[i].first, b[j].first, c[k].first });
                if (cur_pos > cnt - x) break;
                if (a[i].first == cur_pos) {
                    vala = a[i].second;
                    ++i;
                }
                if (b[j].first == cur_pos) {
                    valb = b[j].second;
                    ++j;
                }
                if (c[k].first == cur_pos) {
                    valc = c[k].second;
                    ++k;
                }
                int mn = vala;
                if (mn == -1 or (valb != -1 and pos[cnt][mn] > pos[cnt][valb])) {
                    mn = valb;
                }
                if (mn == -1 or (valc != -1 and pos[cnt][mn] > pos[cnt][valc])) {
                    mn = valc;
                }
                if (mn != last_min) {
                    ndp[x][biba++] = make_pair(cur_pos, mn);
                    last_min = mn;
                }
            }
            ndp[x][biba++] = make_pair(10 * n + 10000, -1);
            assert(biba <= 9);
        }
        dp.swap(ndp);
    }
    assert(!dp.empty() and !dp[0].empty());
    int result = -1;
    for (auto [cur_pos, cur_val] : dp[0]) {
        if (cur_pos <= 0) {
            result = cur_val;
        } else {
            break;
        }
    }
    cout << result + 1 << "\n";
    return 0;
}