Problem: This is the hard version of the problem. The difference between the versions is in the number of possible operations that can be made. You can make hacks if and only if you solved both versions of the problem.

You are given a binary table of size n × m. This table consists of symbols 0 and 1.

You can make such operation: select 3 different cells that belong to one 2 × 2 square and change the symbols in these cells (change 0 to 1 and 1 to 0).

Your task is to make all symbols in the table equal to 0. You are allowed to make at most nm operations. You don't need to minimize the number of operations.

It can be proved, that it is always possible.

Input

The first line contains a single integer t (1 ≤ t ≤ 5000) — the number of test cases. The next lines contain descriptions of test cases.

The first line of the description of each test case contains two integers n, m (2 ≤ n, m ≤ 100).

Each of the next n lines contains a binary string of length m, describing the symbols of the next row of the table.

It is guaranteed, that the sum of nm for all test cases does not exceed 20000.

Output

For each test case print the integer k (0 ≤ k ≤ nm) — the number of operations.

In the each of the next k lines print 6 integers x_1, y_1, x_2, y_2, x_3, y_3 (1 ≤ x_1, x_2, x_3 ≤ n, 1 ≤ y_1, y_2, y_3 ≤ m) describing the next operation. This operation will be made with three cells (x_1, y_1), (x_2, y_2), (x_3, y_3). These three cells should be different. These three cells should belong to some 2 × 2 square.

Example

Input


5
2 2
10
11
3 3
011
101
110
4 4
1111
0110
0110
1111
5 5
01011
11001
00010
11011
10000
2 3
011
101


Output


1
1 1 2 1 2 2
2 
2 1 3 1 3 2
1 2 1 3 2 3
4
1 1 1 2 2 2 
1 3 1 4 2 3
3 2 4 1 4 2
3 3 4 3 4 4
4
1 2 2 1 2 2 
1 4 1 5 2 5 
4 1 4 2 5 1
4 4 4 5 3 4
2
1 3 2 2 2 3
1 2 2 1 2 2

Note

In the first test case, it is possible to make only one operation with cells (1, 1), (2, 1), (2, 2). After that, all symbols will be equal to 0.

In the second test case:

  * operation with cells (2, 1), (3, 1), (3, 2). After it the table will be: 
    
          
    011  
    001  
    000  
    

  * operation with cells (1, 2), (1, 3), (2, 3). After it the table will be: 
    
          
    000  
    000  
    000  
    




In the fifth test case:

  * operation with cells (1, 3), (2, 2), (2, 3). After it the table will be: 
    
          
    010  
    110  
    

  * operation with cells (1, 2), (2, 1), (2, 2). After it the table will be: 
    
          
    000  
    000  
    

Solution (in JAVA):

Solution:


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Random;
import java.util.StringTokenizer;

public final class D {

    private static void f(int[][] grid, int row, int col, int[] count, StringBuilder pw) {
        final int upL = grid[row][col];
        final int upR = grid[row][col + 1];
        final int downL = grid[row + 1][col];
        final int downR = grid[row + 1][col + 1];
        final int sum = upL + upR + downL + downR;
        if (sum == 1) {
            f1(grid, row, col, count, pw);
        } else if (sum == 2) {
            f2(grid, row, col, count, pw);
        } else if (sum == 3) {
            f3(grid, row, col, count, pw);
        } else {
            f4(grid, row, col, count, pw);
        }
    }

    private static void f1(int[][] grid, int row, int col, int[] count, StringBuilder pw) {
        final int upL = grid[row][col];
        final int upR = grid[row][col + 1];
        final int downL = grid[row + 1][col];
        if (upL == 1) {
            update(grid, row, col, row + 1, col, row + 1, col + 1, count, pw);
            f2(grid, row, col, count, pw);
        } else if (upR == 1) {
            update(grid, row, col + 1, row + 1, col, row + 1, col + 1, count, pw);
            f2(grid, row, col, count, pw);
        } else if (downL == 1) {
            update(grid, row, col, row, col + 1, row + 1, col, count, pw);
            f2(grid, row, col, count, pw);
        } else {
            update(grid, row, col, row, col + 1, row + 1, col + 1, count, pw);
            f2(grid, row, col, count, pw);
        }
    }

    private static void f2(int[][] grid, int row, int col, int[] count, StringBuilder pw) {
        final int upL = grid[row][col];
        final int upR = grid[row][col + 1];
        final int downL = grid[row + 1][col];
        final int downR = grid[row + 1][col + 1];
        if (upL == 1 && upR == 1) {
            update(grid, row, col + 1, row + 1, col, row + 1, col + 1, count, pw);
            f3(grid, row, col, count, pw);
        } else if (upL == 1 && downL == 1) {
            update(grid, row, col + 1, row + 1, col, row + 1, col + 1, count, pw);
            f3(grid, row, col, count, pw);
        } else if (upL == 1 && downR == 1) {
            update(grid, row, col, row, col + 1, row + 1, col, count, pw);
            f3(grid, row, col, count, pw);
        } else if (upR == 1 && downR == 1) {
            update(grid, row, col, row, col + 1, row + 1, col, count, pw);
            f3(grid, row, col, count, pw);
        } else if (upR == 1 && downL == 1) {
            update(grid, row, col, row + 1, col, row + 1, col + 1, count, pw);
            f3(grid, row, col, count, pw);
        } else if (downL == 1 && downR == 1) {
            update(grid, row, col, row, col + 1, row + 1, col + 1, count, pw);
            f3(grid, row, col, count, pw);
        }
    }

    private static void f3(int[][] grid, int row, int col, int[] count, StringBuilder pw) {
        final int upL = grid[row][col];
        final int upR = grid[row][col + 1];
        final int downL = grid[row + 1][col];
        if (upL == 0) {
            update(grid, row, col + 1, row + 1, col, row + 1, col + 1, count, pw);
        } else if (upR == 0) {
            update(grid, row, col, row + 1, col, row + 1, col + 1, count, pw);
        } else if (downL == 0) {
            update(grid, row, col, row, col + 1, row + 1, col + 1, count, pw);
        } else {
            update(grid, row, col, row, col + 1, row + 1, col, count, pw);
        }
    }

    private static void f4(int[][] grid, int row, int col, int[] count, StringBuilder pw) {
        update(grid, row, col, row + 1, col, row + 1, col + 1, count, pw);
        f1(grid, row, col, count, pw);
    }

    private static void shiftLeft(int[][] grid, int row, int col, int[] count, StringBuilder pw) {
        final int upL = grid[row][col];
        final int downL = grid[row + 1][col];
        if (upL == 1 && downL == 0) {
            update(grid, row, col, row, col + 1, row + 1, col + 1, count, pw);
        } else if (upL == 0 && downL == 1) {
            update(grid, row + 1, col, row, col + 1, row + 1, col + 1, count, pw);
        } else if (upL == 1 && downL == 1) {
            update(grid, row, col, row + 1, col, row + 1, col + 1, count, pw);
        }
    }

    private static void shiftDown(int[][] grid, int row, int col, int[] count, StringBuilder pw) {
        final int upL = grid[row][col];
        final int upR = grid[row][col + 1];
        if (upL == 1 && upR == 0) {
            update(grid, row, col, row + 1, col, row + 1, col + 1, count, pw);
        } else if (upL == 0 && upR == 1) {
            update(grid, row, col + 1, row +1, col, row + 1, col + 1, count, pw);
        } else if (upL == 1 && upR == 1) {
            update(grid, row, col, row, col + 1, row + 1, col + 1, count, pw);
        }
    }

    private static void update(int[][] grid, int r1, int c1, int r2, int c2, int r3, int c3, int[] count,
                               StringBuilder pw) {
        count[0]++;
        grid[r1][c1] ^= 1;
        grid[r2][c2] ^= 1;
        grid[r3][c3] ^= 1;
        pw.append(r1 + 1);
        pw.append(' ');
        pw.append(c1 + 1);
        pw.append(' ');
        pw.append(r2 + 1);
        pw.append(' ');
        pw.append(c2 + 1);
        pw.append(' ');
        pw.append(r3 + 1);
        pw.append(' ');
        pw.append(c3 + 1);
        pw.append('\n');
    }

    public static void main(String[] args) {
        final FastScanner fs = new FastScanner();
        final int t = fs.nextInt();
        for (int test = 0; test < t; test++) {
            final int n = fs.nextInt();
            final int m = fs.nextInt();
            final int[][] grid = new int[n][m];
            for (int i = 0; i < n; i++) {
                final String line = fs.next();
                for (int j = 0; j < m; j++) {
                    grid[i][j] = line.charAt(j) == '1' ? 1 : 0;
                }
            }
            final StringBuilder sb = new StringBuilder();
            final int[] count = { 0 };
            for (int i = 0; i < n; i += 2) {
                if (i == (n - 1)) {
                    i--;
                }
                for (int j = 0; j < m - 2; j++) {
                    shiftLeft(grid, i, j, count, sb);
                }
            }
            for (int i = 0; i < n - 2; i++) {
                shiftDown(grid, i, m - 2, count, sb);
            }
            f(grid, n - 2, m - 2, count, sb);
            sb.deleteCharAt(sb.length() - 1);
            System.out.println(count[0]);
            System.out.println(sb);
        }
    }

    static final class Utils {
        public static void shuffleSort(int[] x) {
            shuffle(x);
            Arrays.sort(x);
        }

        public static void shuffleSort(long[] x) {
            shuffle(x);
            Arrays.sort(x);
        }

        public static void shuffle(int[] x) {
            final Random r = new Random();

            for (int i = 0; i <= x.length - 2; i++) {
                final int j = i + r.nextInt(x.length - i);
                swap(x, i, j);
            }
        }

        public static void shuffle(long[] x) {
            final Random r = new Random();

            for (int i = 0; i <= x.length - 2; i++) {
                final int j = i + r.nextInt(x.length - i);
                swap(x, i, j);
            }
        }

        public static void swap(int[] x, int i, int j) {
            final int t = x[i];
            x[i] = x[j];
            x[j] = t;
        }

        public static void swap(long[] x, int i, int j) {
            final long t = x[i];
            x[i] = x[j];
            x[j] = t;
        }

        private Utils() {}
    }

    static class FastScanner {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

        private String next() {
            while (!st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    //noinspection CallToPrintStackTrace
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        int[] nextIntArray(int n) {
            final int[] a = new int[n];
            for (int i = 0; i < n; i++) { a[i] = nextInt(); }
            return a;
        }

        long[] nextLongArray(int n) {
            final long[] a = new long[n];
            for (int i = 0; i < n; i++) { a[i] = nextLong(); }
            return a;
        }
    }
}