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

using namespace std;
inline int r() {
	int x = 0;
	char c = getchar(); // Windows-on getchar(), Linux-on getchar_unlocked() még gyorsabb

	while (c < '0' || c > '9') {
		c = getchar();
	}

	while (c >= '0' && c <= '9') {
		x = (x << 3) + (x << 1) + (c - '0');
		c = getchar();
	}
	return x;
}

struct tomb
{
	int a;
	int b;
};
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	int n, m, k;
	n = r(); m = r(); k = r();
	tomb x;
	vector<tomb> t;
	vector<tomb> meg;
	for (int i = 0; i < m; ++i)
	{
		x.b = r();
		x.a = i + 1;
		t.push_back(x);
	}
	sort(t.begin(), t.end(), [](const tomb& g, const tomb& h) { return g.b < h.b; });
	int szam = 0;
	for (int nap = 1; nap <= n; ++nap)
	{
		for (int i = 0; i < k and szam < m; ++i)
		{
			if (t[szam].b >= nap)
			{
				t[szam].b = nap;
				meg.push_back(t[szam]);
				++szam;
			}
			else
			{
				while (!(t[szam].b >= nap) and szam < m) ++szam;
				if (szam < m)
				{
					t[szam].b = nap;
					meg.push_back(t[szam]);
					++szam;
				}
			}
		}
	}
	cout << meg.size() << endl;
	for (int i = 0; i < meg.size(); ++i) cout << meg[i].a << " " << meg[i].b << "\n";
	return 0;
}