#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;

const int INF = (int)1e6;
int m = 1010;
int del, k;
int n;
int it1, it2;
int a[55];
int dp[1010][52][52][3];
int ans[55][2];

int main()
{
    scanf("%d%d", &del, &k);
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
        scanf("%d", &a[i]);
    for (int i = 0; i < m; i++)
        for (int j = 0; j <= n; j++)
            for (int h = 0; h <= n; h++)
                dp[i][j][h][0] = INF;
    dp[0][0][0][0] = 0;
    for (int tm = 0; tm < m; tm++)
    {
        while (it1 < n && a[it1] - del <= tm)
            it1++;
        while (it2 < n && a[it2] <= tm)
            it2++;
        for (int frst = 0; frst <= it1; frst++)
            for (int scnd = it2; scnd <= frst; scnd++)
            {
                if (dp[tm][frst][scnd][0] == INF)
                    continue;
                if (dp[tm + 1][frst][scnd][0] > dp[tm][frst][scnd][0])
                {
                    dp[tm + 1][frst][scnd][0] = dp[tm][frst][scnd][0];
                    dp[tm + 1][frst][scnd][1] = frst;
                    dp[tm + 1][frst][scnd][2] = scnd;
                }
                int w = dp[tm][frst][scnd][0] + 1;
                if (k >= it1 - scnd)
                {
                    if (dp[tm + 1][it1][frst][0] > w)
                    {
                        dp[tm + 1][it1][frst][0] = w;
                        dp[tm + 1][it1][frst][1] = frst;
                        dp[tm + 1][it1][frst][2] = scnd;
                    }
                }
                else
                {
                    for (int i = max( 0, k - (it1 - frst) ); i <= min(k, frst - scnd)  ; i++)
                    {
                        if (dp[tm + 1][frst + k - i][scnd + i][0] > w)
                        {
                            dp[tm + 1][frst + k - i][scnd + i][0] = w;
                            dp[tm + 1][frst + k - i][scnd + i][1] = frst;
                            dp[tm + 1][frst + k - i][scnd + i][2] = scnd;
                        }
                    }
                }
            }
    }

    m--;
    if (dp[m][n][n][0] == INF)
    {
        printf("-1\n");
        return 0;
    }
    printf("%d\n", dp[m][n][n][0]);

    int f = n, s = n;
    for (; m > 0; m--)
    {
        int nf = dp[m][f][s][1];
        int ns = dp[m][f][s][2];
        for (int i = nf; i < f; i++)
            ans[i][0] = m - 1;
        for (int i = ns; i < s; i++)
            ans[i][1] = m - 1;
        f = nf;
        s = ns;
    }
    for (int i = 0; i < n; i++)
        printf("%d %d\n", ans[i][0], ans[i][1]);

    cin >> n;
    return 0;
}