#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
	int n, m, k; cin >> n >> m >> k;
	vector<pair<int, int>> v(m);
	vector<pair<int, int>> x;

	for (int i = 0; i < m; ++i) {
		cin >> v[i].first;
		v[i].second = i + 1;
	}

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

	int nap = 1, db = 0, t = 0;
	for (int i = 0; i < m; ++i) {
		if (db < k && v[i].first >= nap) {
			++db;
			++t;

			x.push_back({ v[i].second, nap });
		}
		else if (db == k) {
			++nap;
			db = 0;
			
			--i;
		}
	}

	cout << t << "\n";
	for (auto &e : x) {
		cout << e.first << " " << e.second << "\n";
	}
}