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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.ArrayList;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Pranay2516
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader in = new FastReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C2BinaryTableHardVersion solver = new C2BinaryTableHardVersion();
        int testCount = Integer.parseInt(in.next());
        for (int i = 1; i <= testCount; i++)
            solver.solve(i, in, out);
        out.close();
    }

    static class C2BinaryTableHardVersion {
        int[][] a;

        public void solve(int testNumber, FastReader in, PrintWriter out) {
            int n = in.nextInt(), m = in.nextInt();
            char[][] c = new char[n][m];
            a = new int[n][m];
            ArrayList<Points> ans = new ArrayList<Points>();
            for (int i = 0; i < n; ++i) c[i] = in.next().toCharArray();
            for (int i = 0; i < n; ++i) {
                for (int j = 0; j < m; ++j) {
                    a[i][j] = c[i][j] - 48;
                }
            }
            for (int j = m - 1; j > 1; --j) {
                for (int i = 0; i < n; ++i) {
                    if (a[i][j] == 1) {
                        if (i + 1 < n) {
                            ans.add(new Points(i, j, i, j - 1, i + 1, j));
                            a[i][j - 1] = a[i][j - 1] > 0 ? 0 : 1;
                            a[i + 1][j] = a[i + 1][j] > 0 ? 0 : 1;
                        } else {
                            ans.add(new Points(i, j, i, j - 1, i - 1, j - 1));
                            a[i][j - 1] = a[i][j - 1] > 0 ? 0 : 1;
                            a[i - 1][j - 1] = a[i - 1][j - 1] > 0 ? 0 : 1;
                        }
                        a[i][j] = 0;
                    }
                }
            }
            if (n % 2 == 1) {
                if (a[n - 1][0] + a[n - 1][1] == 2) {
                    ans.add(new Points(n - 1, 0, n - 1, 1, n - 2, 0));
                    a[n - 2][0] = a[n - 2][0] > 0 ? 0 : 1;
                } else if (a[n - 1][0] == 1) {
                    ans.add(new Points(n - 1, 0, n - 2, 0, n - 2, 1));
                    a[n - 2][0] = a[n - 2][0] > 0 ? 0 : 1;
                    a[n - 2][1] = a[n - 2][1] > 0 ? 0 : 1;
                } else if (a[n - 1][1] == 1) {
                    ans.add(new Points(n - 1, 1, n - 2, 0, n - 2, 1));
                    a[n - 2][0] = a[n - 2][0] > 0 ? 0 : 1;
                    a[n - 2][1] = a[n - 2][1] > 0 ? 0 : 1;
                }
                a[n - 1][0] = 0;
                a[n - 1][1] = 0;
            }
            for (int i = 0; i < n - 1; i += 2) {
                int j = 0;
                int g = checkPoints(i, j);
                if (g == 0) {
                } else if (g == 1) {
                    int l = 0, k = 0;
                    if (a[i][j] == 1) {
                        ans.add(new Points(i, j, i, j + 1, i + 1, j));
                        ans.add(new Points(i, j, i, j + 1, i + 1, j + 1));
                        ans.add(new Points(i, j, i + 1, j, i + 1, j + 1));
                    } else if (a[i][j + 1] == 1) {
                        ans.add(new Points(i, j, i, j + 1, i + 1, j + 1));
                        ans.add(new Points(i, j, i, j + 1, i + 1, j));
                        ans.add(new Points(i, j + 1, i + 1, j, i + 1, j + 1));
                    } else if (a[i + 1][j] == 1) {
                        ans.add(new Points(i + 1, j, i + 1, j + 1, i, j));
                        ans.add(new Points(i + 1, j, i, j + 1, i, j));
                        ans.add(new Points(i, j + 1, i + 1, j, i + 1, j + 1));
                    } else if (a[i + 1][j + 1] == 1) {
                        ans.add(new Points(i + 1, 1 + j, i + 1, j, i, j + 1));
                        ans.add(new Points(i + 1, 1 + j, i, 1 + j, i, j));
                        ans.add(new Points(i, j, i + 1, j, i + 1, j + 1));
                    }
                } else if (g == 2) {
                    if (a[i][j] + a[i + 1][j] == 2 || a[i][j] + a[i][j + 1] == 2 || a[i + 1][j] + a[i + 1][j + 1] == 2 || a[i][j + 1] + a[i + 1][j + 1] == 2) {
                        if (a[i][j] == 1) {
                            if (a[i][j + 1] == 1) {
                                ans.add(new Points(i, j, i + 1, j, i + 1, j + 1));
                                ans.add(new Points(i, j + 1, i + 1, j + 1, i + 1, j));
                            } else if (a[i + 1][j] == 1) {
                                ans.add(new Points(i, j, i, j + 1, i + 1, j + 1));
                                ans.add(new Points(i, j + 1, i + 1, j, i + 1, j + 1));
                            }
                        } else if (a[i + 1][j + 1] == 1) {
                            if (a[i + 1][j] == 1) {
                                ans.add(new Points(i, j, i, j + 1, i + 1, j));
                                ans.add(new Points(i, j, i, j + 1, i + 1, j + 1));
                            } else if (a[i][j + 1] == 1) {
                                ans.add(new Points(i, j, i + 1, j, i + 1, j + 1));
                                ans.add(new Points(i, j, i, j + 1, i + 1, j));
                            }
                        }
                    } else if (a[i][j] + a[i + 1][j + 1] == 2 || a[i + 1][j] + a[i][j + 1] == 2) {
                        if (a[i][j] == 1) {
                            ans.add(new Points(i, j + 1, i + 1, j, i + 1, j + 1));
                            ans.add(new Points(i, j, i, j + 1, i + 1, j));
                        } else {
                            ans.add(new Points(i, j, i, j + 1, i + 1, j + 1));
                            ans.add(new Points(i, j, i + 1, j, i + 1, j + 1));
                        }
                    }
                } else if (g == 3) {
                    int k = 0, l = 0, e = 0;
                    Pair<Integer, Integer>[] p = new Pair[3];
                    for (k = 0; k < 2; ++k) {
                        for (l = 0; l < 2; ++l) {
                            if (a[i + k][j + l] == 1) {
                                p[e] = new Pair<>(i + k, l + j);
                                e++;
                            }
                        }
                    }
                    ans.add(new Points(p[0].x, p[0].y, p[1].x, p[1].y, p[2].x, p[2].y));
                } else if (g == 4) {
                    ans.add(new Points(i, j, i + 1, j, i, j + 1));
                    ans.add(new Points(i + 1, j + 1, i + 1, j, i, j + 1));
                    ans.add(new Points(i + 1, j + 1, i, j + 1, i, j));
                    ans.add(new Points(i, j, i + 1, j, i + 1, j + 1));
                }
                putzero(i, j);
            }
            out.println(ans.size());
            for (Points e : ans) {
                out.println((e.x1 + 1) + " " + (e.y1 + 1) + " " + (e.x2 + 1) + " " + (e.y2 + 1) + " " + (e.x3 + 1) + " " + (e.y3 + 1));
            }
        }

        int checkPoints(int i, int j) {
            return a[i][j] + a[i + 1][j + 1] + a[i + 1][j] + a[i][j + 1];
        }

        void putzero(int i, int j) {
            a[i][j] = a[i + 1][j] = a[i][j + 1] = a[i + 1][j + 1] = 0;
        }

        class Points {
            int x1;
            int y1;
            int x2;
            int y2;
            int x3;
            int y3;

            public Points(int x1, int y1, int x2, int y2, int x3, int y3) {
                this.x1 = x1;
                this.y1 = y1;
                this.x2 = x2;
                this.y2 = y2;
                this.x3 = x3;
                this.y3 = y3;
            }

        }

    }

    static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private FastReader.SpaceCharFilter filter;

        public FastReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) return -1;
            }
            return buf[curChar++];
        }

        public int nextInt() {
            int c = read();
            while (isSpaceChar(c)) c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }

        public String next() {
            int c = read();
            while (isSpaceChar(c)) c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class Pair<U, V> implements Comparable<Pair<U, V>> {
        public U x;
        public V y;

        public Pair(U x, V y) {
            this.x = x;
            this.y = y;
        }

        public int compareTo(Pair<U, V> o) {
            int value = ((Comparable<U>) x).compareTo(o.x);
            if (value != 0) return value;
            return ((Comparable<V>) y).compareTo(o.y);
        }

    }
}