// Megrendelések.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n, m, k;
    cin >> n >> m >> k;
    vector<pair<int, int>> rendelesek(m + 1);
    for (int i = 1; i <= m; i++) {
        int x;
        cin >> x;
        rendelesek[i] = { x,i };
    }
    sort(rendelesek.begin()+1, rendelesek.end());
    vector<pair<int, int>> res;
    int hol = 1;
    for (int i = 1; i <= n; i++)
    {
        while (hol <= m && rendelesek[hol].first < i)
        {
            hol++;
        }
        int maxdb = k;
        while (hol<=m and maxdb > 0 and i <= rendelesek[hol].first)
        {
            res.push_back({ rendelesek[hol].second,i });
            hol++;
            maxdb--;
        }
    }
    cout << res.size()<<endl;
    for (auto x : res)
        cout << x.first << " " << x.second << endl;
}

// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu

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//   6. In the future, to open this project again, go to File > Open > Project and select the .sln file