#include <bits/stdc++.h>

#define el '\n'

typedef long long ll;
typedef long double ld;

#define Beevo ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

using namespace std;

const int N = 1e3 + 5;

int n;
vector<int> v[N];
vector<pair<int, int>> op;

void clean(int i) {
    while (v[i].size()) {
        for (int j = i - 1; j >= 0; j--) {
            if (v[j].size() < 3) {
                op.emplace_back(i + 1, j + 1);

                v[j].push_back(v[i].back()), v[i].pop_back();

                break;
            }
        }
    }
}

int search(int i) {
    vector<int> p(n + 1, 1);

    for (int j = i - 1; j >= 0; j--)
        p[v[j].back()] *= 2, p[v[j][1]] *= 3;

    for (int j = 1; j <= n; j++) {
        if (p[j] >= 4 && p[j] % 2 == 0)
            return j;
    }

    return -1;
}

bool searchTop(int color, int i) {
    for (int j = i - 1; j >= 0; j--) {
        if (v[j].back() == color) {
            v[i].push_back(color), v[j].pop_back();

            op.emplace_back(j + 1, i + 1);

            return 1;
        }
    }

    return 0;
}

bool searchMid(int color, int i) {
    for (int j = i - 1; j >= 0; j--) {
        if (v[j].size() == 3 && v[j][1] == color) {
            for (int k = 0; k < i; k++) {
                if (k == j)
                    continue;

                if (v[k].size() < 3) {
                    v[k].push_back(v[j].back()), v[j].pop_back();

                    op.emplace_back(j + 1, k + 1);

                    break;
                }
            }

            v[i].push_back(color), v[j].pop_back();

            op.emplace_back(j + 1, i + 1);

            return 1;
        }
    }

    return 0;
}

bool searchBot(int color, int i) {
    for (int j = i - 1; j >= 0; j--) {
        if (v[j][0] == color) {
            while (v[j].size() > 1) {
                for (int k = 0; k < i; k++) {
                    if (k == j)
                        continue;

                    if (v[k].size() < 3) {
                        v[k].push_back(v[j].back()), v[j].pop_back();

                        op.emplace_back(j + 1, k + 1);

                        break;
                    }
                }
            }

            v[i].push_back(color), v[j].pop_back();

            op.emplace_back(j + 1, i + 1);

            return 1;
        }
    }

    return 0;
}

void testCase() {
    cin >> n;

    for (int i = 0; i <= n; i++) {
        for (int j = 0, a; j < 3; j++)
            cin >> a, v[i].push_back(a);

        while (v[i].size() && !v[i].back())
            v[i].pop_back();
    }

    for (int i = n; i >= 0; i--) {
        clean(i);

        int color = search(i);

        while (v[i].size() < 3 && searchTop(color, i)) {}

        while (v[i].size() < 3 && searchMid(color, i)) {}

        while (v[i].size() < 3 && searchBot(color, i)) {}
    }

    cout << op.size() << el;

    for (auto &i: op)
        cout << i.first << ' ' << i.second << el;
}

signed main() {
    Beevo

    int t = 1;
//    cin >> t;

    while (t--)
        testCase();
}