/**
 * Author: Daniel
 * Created Time: 2021-03-13 13:41:37
**/

// time-limit: 2000
#include <bits/stdc++.h>

using namespace std;

#define F first 
#define S second
#define ER erase
#define IS insert
#define PI acos(-1)
#define PB pop_back
#define EB emplace_back
#define lowbit(x) (x & -x)
#define SZ(x) ((int)x.size())
#define MP(x, y) make_pair(x, y)
#define ALL(x) x.begin(), x.end()
#define RALL(x) x.rbegin(), x.rend()
#define SOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);cout<<fixed<<setprecision(10)

typedef long long LL;
typedef vector<LL> VL;
typedef vector<int> VI;
typedef pair<LL, LL> PLL;
typedef pair<int, int> PII;
typedef unsigned long long ULL;
typedef pair<double, double> PDD;
typedef vector<pair<int, int> > VPII;

template <typename A> using VE = vector<A>;
template <typename A> using USET = unordered_set<A>;
template <typename A> using HEAP = priority_queue<A>;
template <typename A, typename B> using PA = pair<A, B>;
template <typename A, typename B> using UMAP = unordered_map<A, B>;
template <typename A> using RHEAP = priority_queue<A, vector<A>, greater<A> >;

template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) { return '"' + s + '"'; }

string to_string(const char* s) { return to_string((string)s); } 

string to_string(const char c) { return to_string((string)"" + c); } 

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) 
{
    bool first = true;
    string res = "{";
    for (int i = 0; i < static_cast<int>(v.size()); i++) 
    {
        if (!first) res += ", ";
        first = false;
        res += to_string(v[i]);
    }
    res += "}";
    return res;
}

template <size_t N>
string to_string(bitset<N> v)
{
    string res = "";
    for (size_t i = 0; i < N; i++) res += static_cast<char>('0' + v[i]);
    return res;
}

template <typename A>
string to_string(A v)
{
    bool first = true;
    string res = "{";
    for (const auto &x : v)
    {
        if (!first) res += ", ";
        first = false;
        res += to_string(x);
    }
    res += "}";
    return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) { return "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; }

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) { return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")"; }

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) { return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")"; }

void debug_out() { cout << '\n'; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) { cout << " " << to_string(H); debug_out(T...); }

#ifdef LOCAL
#define debug(...) cout << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

///////////////////////////////////////////////////////////////////////////
//////////////////// DO NOT TOUCH BEFORE THIS LINE ////////////////////////
///////////////////////////////////////////////////////////////////////////

// check the limitation!!!
const int N = 5010, M = 1010;

int n;
int a[N][N];
int res[N];
int p[N];
struct Node
{
    int u, v, val;
    bool operator<(const Node &t) const
    {
        if (val != t.val) return val < t.val;
        else return u < t.u;
    }
};

int find(int x)
{
    if (x != p[x]) p[x] = find(p[x]);
    return p[x];
}

// read the question carefully!!!
int main()
{
    SOS;

    cin >> n;
    for (int i = 1; i <= n; i ++ )
        for (int j = 1; j <= n; j ++ )
            cin >> a[i][j];
    VE<Node> b;
    for (int i = 1; i <= n; i ++ )
        for (int j = i; j <= n; j ++ )
            b.EB((Node){i, j, a[i][j]});
    sort(ALL(b));
    VPII edge;
    int m = n;
    for (int i = 1; i <= n; i ++ ) 
    {
        p[i] = i;
        res[i] = a[i][i];
    }
    for (auto [u, v, val] : b)
    {
        int pa = find(u), pb = find(v);
        if (pa == pb) continue;
        else if (val == res[pb])
        {
            p[pa] = pb;
            edge.EB(pa, pb);
        }
        else if (val == res[pa])
        {
            p[pb] = pa;
            edge.EB(pb, pa);
        }
        else
        {
            p[pa] = p[pb] = ++ m;
            p[m] = m;
            res[m] = val;
            edge.EB(pa, m);
            edge.EB(pb, m);
        }
    }
    cout << m << '\n';
    for (int i = 1; i <= m; i ++ )
    {
        cout << res[i];
        cout << " \n"[i == m];
    }
    cout << find(1) << '\n';
    for (auto [x, y] : edge) cout << x << ' ' << y << '\n';
    return 0;
}

// GOOD LUCK!!!
