//#include <iostream>
#include <algorithm>
#include <fstream>

int STR_LENGHT,STR_N;
std::string w_string;
std::string arr_temp[1000];

std::string arr_string_s[1000];
std::string arr_string_t[1000];

int c_min(int a, int b) {return (a < b) ? a : b;}

bool is_target()
{
	for(int i=0; i<STR_N; ++i)
	{
		arr_temp[i] = "";
		for(int j=0; j<STR_LENGHT; ++j)
        {
			if(w_string[j] == '1')
            {
				arr_temp[i] += 1 - (arr_string_s[i][j]-'0') + '0';
            }
            else
			{
            	arr_temp[i] += arr_string_s[i][j];
            }
        }
	}

	sort(arr_temp, arr_temp + STR_N);

	for(int i=0; i<STR_N; ++i)
    {	
        if(arr_temp[i] != arr_string_t[i])
			return false;
	}
    return true;
}

int main(int argc, char** argv)
{
	int min_moves = -1;
    int moves;

    std::ifstream fin("input.txt");
    std::ofstream fout("output.txt");

    fin >> STR_N >> STR_LENGHT ;

	for(int i=0; i<STR_N; ++i)
    {
		fin >> arr_string_s[i];
    }

	for(int i=0; i<STR_N; ++i)
    {
		fin >> arr_string_t[i];
    }

	sort(arr_string_t, arr_string_t+STR_N);

	for(int i=0; i<STR_N; ++i)
	{
    	w_string = "";
	    moves = 0;

	    for(int k=0; k<STR_LENGHT; ++k)
        {
		    if(arr_string_s[0][k] == arr_string_t[i][k])
            {
			    w_string.append("0");
            }
		    else
		    {
			    moves++;
			    w_string.append("1");
		    }
        }

		if(is_target() == true)
        {
	        if(min_moves == -1)
	        {
                min_moves = moves;
            }
            else
            {
                min_moves = c_min(min_moves, moves);
            }			
        }
	}

	if(min_moves == -1)
    {
		fout << "NOT POSSIBLE";
    }
	else
    {
		fout << min_moves;
    }
 
	return 0;
}