#include <iostream>
#include <cstdint>
#include <algorithm>

#include <vector>
#include <set>
#include <map>
#include <queue>

using namespace std;

typedef int64_t ll;

void cerrr(vector<pair<ll,ll>> v) {
    for(const auto [x ,y] : v) {
        cerr << "{" << x << "," << y << "},";
    }
}

void solve() {

    ll n, m, k;
    cin >> n >> m >> k;

    vector<pair<ll,ll>> v(m, {0,0});

    for(ll i = 1; i <= m; i++) {
        ll deadline;
        cin >> deadline;
        v[i-1] = {deadline, i};
    }

    vector<pair<ll,ll>> res;

    sort(v.begin(), v.end());

    //cerr << "\nv=";
    //cerrr(v);

    ll j = 0;
    for(ll d = 1; d <= n; d++) {

        //cerr << "\nd=" << d;

        ll hd = 0;
        while(j < m && hd < k) {

            while(j < m && v[j].first < d) {
                j++;
            }

            if(j == m) {
                break;
            }

            //cerr << "\nj=" << j << "; hd=" << hd;
            //err << "\nv[j].second, d=" << v[j].second << " " << d;

            res.push_back({v[j].second, d});
            j++;
            hd++;
        }
    }

    cout << res.size() << "\n";
    for(const auto & x : res) {
        cout << x.first << " " << x.second << "\n";
    }

}

int main() {
    
    std::ios_base::sync_with_stdio(false);
    
    solve();
    
    return 0;

}