#include<bits/stdc++.h>
using namespace std;

template<typename X, typename Y>
bool chmax(X& a, Y b) { return (a < b) ? a = b, 1 : 0; }

template<typename X, typename Y>
bool chmin(X& a, Y b) { return (a > b) ? a = b, 1 : 0; }

using ll = long long;
using pii = pair<int, int>;

const int N = 1e4+5;

int n, d[N];

void solve() {
    cin >> n;
    vector<pii> nodes;
    for (int i = 1; i <= n; i++) {
        cin >> d[i];
        nodes.push_back({d[i], i});
    }
    sort(nodes.begin(), nodes.end(), greater<pii>());
    vector<pii> edges;
    vector<int> connected;
    vector<vector<bool>> adj(n + 5, vector<bool>(n + 5, false));
    connected.push_back(nodes[0].second);
    int j = 0;
    for (int i = 1; i < n; i++) {
        int v = nodes[i].second;
        while (j < (int)connected.size() && d[connected[j]] == 0) j++;
        int u = connected[j];
        edges.push_back({u, v});
        adj[u][v] = adj[v][u] = true;
        d[u]--; d[v]--;
        connected.push_back(v);
    }
    priority_queue<pii> pq;
    for (int i = 1; i <= n; i++)
        if (d[i] > 0) pq.push({d[i], i});
    while (!pq.empty()) {
        auto [d_u, u] = pq.top(); pq.pop();
        if (d_u != d[u]) continue;
        nodes.clear();
        while (d[u] > 0 && !pq.empty()) {
            auto [d_v, v] = pq.top(); pq.pop();
            if (d_v != d[v]) continue;
            if (!adj[u][v]) {
                edges.push_back({u, v});
                adj[u][v] = adj[v][u] = true;
                d[u]--; d[v]--;
            }
            if (d[v] > 0) nodes.push_back({d[v], v});
        }
        for (pii p : nodes) pq.push(p);
    }
    for (pii e : edges) cout << e.first << ' ' << e.second << '\n';
}

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

    #define TASK "MKGRAPH"
    if (fopen(TASK".INP", "r")) {
        freopen(TASK".INP", "r", stdin);
        freopen(TASK".OUT", "w", stdout);
    }

    int tests = 1; // cin >> tests;
    while (tests--) solve();

    #ifdef LOCAL
    cerr << "\nTime elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
    #endif
    return 0;
}