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 PYTHON3):

Solution:
"""
    Author - Satwik Tiwari .
    17th NOV , 2020  - Tuesday
"""

#===============================================================================================
#importing some useful libraries.

from __future__ import division, print_function
from fractions import Fraction
import sys
import os
from io import BytesIO, IOBase
from functools import cmp_to_key

# from itertools import *
from heapq import *
from math import gcd, factorial,floor,ceil,sqrt

from copy import deepcopy
from collections import deque


from bisect import bisect_left as bl
from bisect import bisect_right as br
from bisect import bisect

#==============================================================================================
#fast I/O region
BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


def print(*args, **kwargs):
    """Prints the values to a stream, or to sys.stdout by default."""
    sep, file = kwargs.pop("sep", " "), kwargs.pop("file", sys.stdout)
    at_start = True
    for x in args:
        if not at_start:
            file.write(sep)
        file.write(str(x))
        at_start = False
    file.write(kwargs.pop("end", "\n"))
    if kwargs.pop("flush", False):
        file.flush()


if sys.version_info[0] < 3:
    sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
else:
    sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)

# inp = lambda: sys.stdin.readline().rstrip("\r\n")

#===============================================================================================
### START ITERATE RECURSION ###
from types import GeneratorType
def iterative(f, stack=[]):
  def wrapped_func(*args, **kwargs):
    if stack: return f(*args, **kwargs)
    to = f(*args, **kwargs)
    while True:
      if type(to) is GeneratorType:
        stack.append(to)
        to = next(to)
        continue
      stack.pop()
      if not stack: break
      to = stack[-1].send(to)
    return to
  return wrapped_func
#### END ITERATE RECURSION ####

#===============================================================================================
#some shortcuts

def inp(): return sys.stdin.readline().rstrip("\r\n") #for fast input
def out(var): sys.stdout.write(str(var))  #for fast output, always take string
def lis(): return list(map(int, inp().split()))
def stringlis(): return list(map(str, inp().split()))
def sep(): return map(int, inp().split())
def strsep(): return map(str, inp().split())
# def graph(vertex): return [[] for i in range(0,vertex+1)]
def testcase(t):
    for pp in range(t):
        solve(pp)
def google(p):
    print('Case #'+str(p)+': ',end='')
def lcm(a,b): return (a*b)//gcd(a,b)
def power(x, y, p) :
    y%=(p-1)  #not so sure about this. used when y>p-1. if p is prime.
    res = 1     # Initialize result
    x = x % p  # Update x if it is more , than or equal to p
    if (x == 0) :
        return 0
    while (y > 0) :
        if ((y & 1) == 1) : # If y is odd, multiply, x with result
            res = (res * x) % p

        y = y >> 1      # y = y/2
        x = (x * x) % p
    return res
def ncr(n,r): return factorial(n) // (factorial(r) * factorial(max(n - r, 1)))
def isPrime(n) :
    if (n <= 1) : return False
    if (n <= 3) : return True
    if (n % 2 == 0 or n % 3 == 0) : return False
    i = 5
    while(i * i <= n) :
        if (n % i == 0 or n % (i + 2) == 0) :
            return False
        i = i + 6
    return True
inf = pow(10,20)
mod = 10**9+7
#===============================================================================================
# code here ;))

from random import randint

def solve(case):
    n,m = sep()
    g = []
    for i in range(n):
        temp = list(inp())
        for j in range(len(temp)):
            temp[j] = int(temp[j])

        g.append(temp)

    # n,m = randint(2,10),randint(2,10)
    # g = []
    # for i in range(n):
    #     temp = [randint(0,1) for i in range(m)]
    #     g.append(temp)
    # new = deepcopy(g)
    ans = []
    for i in range(n-1):
        for j in range(m):
            if(i == n-2 and j == m-1 or i==n-2 and j == m-2):
                continue
            if(g[i][j] == 1):
                if(j!=m-1):
                    ans.append((i,i+1,i+1,j,j,j+1))
                    g[i+1][j] = 1-g[i+1][j]
                    g[i+1][j+1] = 1-g[i+1][j+1]
                else:
                    ans.append((i,i+1,i+1,j,j,j-1))
                    g[i+1][j] = 1-g[i+1][j]
                    g[i+1][j-1] = 1-g[i+1][j-1]
    # if(g[n-1][0] == 1):
    #     ans.append()

    # print(len(ans))
    i = n-1
    # print(g[i])
    for j in range(m-2):
        if(g[i][j] == 1):
            if(g[i][j+1] == 0):
                ans.append((i,i,i-1,j,j+1,j+1))
                ans.append((i-1,i,i,j+1,j+1,j+2))
                g[i][j+2] = 1-g[i][j+2]
            else:
                ans.append((i,i-1,i-1,j,j,j+1))
                ans.append((i-1,i-1,i,j,j+1,j+1))
                g[i][j+1] = 0

    # print(len(ans))
    # print(g[i])
    if(g[i-1][m-2] == 0):
        if(g[i][m-2] == 1 and g[i][m-1] == 1):
            if(g[i-1][m-1] == 1):
                ans.append((i-1,i,i,m-1,m-1,m-2))
            else:
                ans.append((i,i-1,i-1,m-2,m-2,m-1))
                ans.append((i-1,i-1,i,m-2,m-1,m-1))

        # print(len(ans))
        if(g[i][m-2] == 0 and g[i][m-1] == 1):
            if(g[i-1][m-1] == 1):
                ans.append((i-1,i,i,m-2,m-2,m-1))
                ans.append((i,i-1,i-1,m-2,m-2,m-1))
            else:
                ans.append((i-1,i,i,m-2,m-2,m-1))
                ans.append((i-1,i-1,i,m-2,m-1,m-1))
                ans.append((i-1,i,i,m-1,m-1,m-2))
        if(g[i][m-2] == 1 and g[i][m-1] == 0):
            if(g[i-1][m-1] == 1):
                ans.append((i-1,i-1,i,m-2,m-1,m-1))
                ans.append((i-1,i,i,m-2,m-2,m-1))
            else:
                ans.append((i-1,i,i,m-2,m-2,m-1))
                ans.append((i-1,i,i,m-1,m-1,m-2))
                ans.append((i-1,i-1,i,m-2,m-1,m-2))
        if(g[i][m-2] == 0 and g[i][m-1] == 0 and g[i-1][m-1] == 1):
            ans.append((i-1,i-1,i,m-1,m-2,m-2))
            ans.append((i-1,i-1,i,m-2,m-1,m-1))
            ans.append((i-1,i,i,m-1,m-1,m-2))
    else:
        if(g[i][m-2] == 1 and g[i][m-1] == 1):
            if(g[i-1][m-1] == 0):
                ans.append((i-1,i,i,m-2,m-2,m-1))
            else:
                ans.append((i-1,i-1,i,m-2,m-1,m-1))
                ans.append((i,i-1,i-1,m-2,m-2,m-1))
                ans.append((i-1,i,i,m-2,m-2,m-1))
                ans.append((i-1,i,i,m-1,m-1,m-2))
        if(g[i][m-2] == 0 and g[i][m-1] == 0):
            if(g[i-1][m-1] == 1):
                ans.append((i-1,i,i,m-2,m-2,m-1))
                ans.append((i-1,i,i,m-1,m-1,m-2))
            else:
                ans.append((i-1,i,i,m-2,m-2,m-1))
                ans.append((i,i-1,i-1,m-2,m-2,m-1))
                ans.append((i-1,i-1,i,m-2,m-1,m-1))
        if(g[i][m-2] == 1 and g[i][m-1] == 0):
            if(g[i-1][m-1] == 1):
                ans.append((i,i-1,i-1,m-2,m-2,m-1))
            else:
                ans.append((i-1,i-1,i,m-2,m-1,m-1))
                ans.append((i,i,i-1,m-2,m-1,m-1))
        if(g[i][m-2] == 0 and g[i][m-1] == 1):
            if(g[i-1][m-1] == 1):
                ans.append((i-1,i-1,i,m-2,m-1,m-1))
            else:
                ans.append((i,i,i-1,m-2,m-1,m-1))
                ans.append((i,i-1,i-1,m-2,m-2,m-1))



    print(len(ans))
    for i in range(len(ans)):
        print(ans[i][0]+1,ans[i][3]+1,ans[i][1]+1,ans[i][4]+1,ans[i][2]+1,ans[i][5]+1)

    # if(len(ans) > n*m):
    #     print(n,m)
    #     for i in range(n):
    #         print(new[i])
    #     print(len(ans))





# testcase(1)
testcase(int(inp()))



"""
4
10 0 0
20 1 0
30 0 1
40 1 1
4 1
2 3
1 3
"""