/*
 * Solution Template for Yet Another Lights Problem
 * 
 * Australian Informatics Olympiad 2023
 * 
 * This file is provided to assist with reading and writing of the input
 * files for the problem. You may modify this file however you wish, or
 * you may choose not to use this file at all.
 */

import java.io.*;

class Solution {

    /* R is the number of rows. */
    private static int R;

    /* C is the number of columns. */
    private static int C;

    /* grid contains the initial state of each light. */
    private static char grid[][] = new char[205][205];

    /*
     * answer should contain the number of cross-flips in your sequence, or -1
     * if it is impossible to turn all the lights on.
     */
    private static int answer;

    /*
     * cross_flips should contain your sequence of cross-flips. For example, if
     * your first cross-flip is (2, 3), then you should set cross_flips[0][0] =
     * 2 and cross_flips[0][1] = 3.
     */
    private static int cross_flips[][] = new int[40005][2];

    /*
     * Read the next token from the input file.
     * Tokens are separated by whitespace, i.e., spaces, tabs and newlines.
     * If end-of-file is reached then an empty string is returned.
     */
    private static String readToken(BufferedReader in) throws IOException {
        StringBuffer ans = new StringBuffer();
        int next;

        /* Skip any initial whitespace. */
        next = in.read();
        while (next >= 0 && Character.isWhitespace((char)next))
            next = in.read();

        /* Read the following token. */
        while (next >= 0 && ! Character.isWhitespace((char)next)) {
            ans.append((char)next);
            next = in.read();
        }

        return ans.toString();
    }

    public static void main(String[] args) throws IOException {
        /* Open the input and output files. */
        BufferedReader input_file = new BufferedReader(new FileReader(
                "yalpin.txt"));
        BufferedWriter output_file = new BufferedWriter(new FileWriter(
                "yalpout.txt"));

        /*
         * Read the values of R, C and the initial state of each light from the
         * input file.
         */
        R = Integer.parseInt(readToken(input_file));
        C = Integer.parseInt(readToken(input_file));
        for (int i = 0; i < R; i++) {
            grid[i] = readToken(input_file).toCharArray();
        }

        /* TODO: This is where you should compute your solution. */

        /*
         * You should store the number of cross-flips in your sequence, or -1
         * if it is impossible, into the variable answer. If it is possible,
         * then your sequence of cross-flips should be stored in the array
         * cross_flips, using indices 0 to answer-1.
         */

        /* Write the answers to the output file. */
        output_file.write(answer + "\n");
        if (answer != -1) {
            for (int i = 0; i < answer; i++) {
                output_file.write(
                        cross_flips[i][0] + " " + cross_flips[i][1] + "\n");
            }
        }

        /* Finally, close the input/output files. */
        input_file.close();
        output_file.close();
    }
}