#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

int devRow(vector<vector<int> > &arr, vector<int> &d, int firstRow, int secondRow);
int devCol(vector<vector<int> > &arr, vector<int> &d, int firstCol, int secondCol);
bool delDevRows(vector<vector<int> > &arr, vector<int> &rc, vector<int> &cc);
bool delDevCols(vector<vector<int> > &arr, vector<int> &rc, vector<int> &cc, vector<char> &cName);
void delDevs(vector<vector<int> > &arr, vector<int> &rc, vector<int> &cc, vector<char> &cName);
void findCov(vector<vector<int> > arr, vector<int> rc, vector<int> cc, vector<char> cName, int prevCol, int h, vector<char> &cov, vector<vector<char> > &res);

int main()
{
	//ifstream in("input.txt");
	int n, m;
	cin >> n >> m;
	vector<vector<int> > arr(n);

	for (int i = 0; i < n; i++)
	{
		arr[i].resize(m);
		for (int j = 0; j < m; j++)
			{
                cin >> arr[i][j];
			}
	}
	//in.close();
	vector<int> rc(n), cc(m);
	vector<char> cName(m);
	for (int i = 0; i < m; i++)
		cName[i] = 'a' + i;
	for (unsigned int i = 0; i < arr.size(); i++)
		for (unsigned int j = 0; j < arr[i].size(); j++)
		{
			rc[i] += arr[i][j];
			cc[j] += arr[i][j];
		}

	delDevs(arr, rc, cc, cName);

	vector<vector<char> > result;
	vector<char> cov;
	findCov(arr, rc, cc, cName, 0, 1, cov, result);


	for (unsigned  int j = 0; j < result[result.size() - 1].size(); j++)
		cout << result[result.size() - 1][j] << " ";
	cout << endl;

	return 0;
}

// functions

int devRow(vector<vector<int> > &arr, vector<int> &d, int firstRow, int secondRow)
{
	int i = (d[firstRow] < d[secondRow]) ? firstRow : secondRow,
		k = (i == firstRow) ? secondRow : firstRow;
	bool res = true;
	for (unsigned int j = 0; j < arr[i].size(); j++)
		if ((arr[i][j] == 1) && (arr[i][j] != arr[k][j]))
			return -1;
	return k;
}

int devCol(vector<vector<int> > &arr, vector<int> &d, int firstCol, int secondCol)
{
	int j = (d[firstCol] < d[secondCol]) ? firstCol : secondCol,
		k = (j == firstCol) ? secondCol : firstCol;
	bool res = true;
	for (unsigned int i = 0; i < arr.size(); i++)
		if ((arr[i][j] == 1) && (arr[i][j] != arr[i][k]))
			return -1;
	return j;
}

bool delDevRows(vector<vector<int> > &arr, vector<int> &rc, vector<int> &cc)
{
	bool res = false;
	for (unsigned int i = 0; i < arr.size(); i++)
		for (unsigned int k = i + 1; k < arr.size(); k++)
		{
			int row = devRow(arr, rc, i, k);
			if (row != -1)
			{
				for (unsigned int j = 0; j < arr[row].size(); j++)
					cc[j] -= arr[row][j];
				arr.erase(arr.begin() + row);
				rc.erase(rc.begin() + row);
				res = true;
				i--;
				break;
			}
		}
	return res;
}

bool delDevCols(vector<vector<int> > &arr, vector<int> &rc, vector<int> &cc, vector<char> &cName)
{
	bool res = false;
	for (unsigned int j = 0; j < arr[0].size(); j++)
		for (unsigned int k = j + 1; k < arr[0].size(); k++)
		{
			int col = devCol(arr, cc, j, k);
			if (col != -1)
			{
				for (unsigned int i = 0; i < arr.size(); i++)
					rc[i] -= arr[i][col];
				for (unsigned int i = 0; i < arr.size(); i++)
					arr[i].erase(arr[i].begin() + col);
				cc.erase(cc.begin() + col);
				cName.erase(cName.begin() + col);
				res = true;
				j--;
				break;
			}
		}
	return res;
}

void delDevs(vector<vector<int> > &arr, vector<int> &rc, vector<int> &cc, vector<char> &cName)
{
	do
	{
		delDevCols(arr, rc, cc, cName);
	} while (delDevRows(arr, rc, cc));
}

void findCov(vector<vector<int> > arr, vector<int> rc, vector<int> cc, vector<char> cName, int prevCol, int h, vector<char> &cov, vector<vector<char> > &res)
{
	if (!(res.empty()) && (h > res[res.size() - 1].size()))
		return;

	if (!cov.empty())
	{
		for (int i = arr.size() - 1; i >= 0; i--)
			if (arr[i][prevCol] == 1)
			{
				for (int j = 0; j < arr[i].size(); j++)
					cc[j] -= arr[i][j];
				arr.erase(arr.begin() + i);
				rc.erase(rc.begin() + i);
			}

		if (arr.empty())
		{
			res.push_back(cov);
			return;
		}

		delDevs(arr, rc, cc, cName);
	}

	int row = min_element(rc.begin(), rc.end()) - rc.begin();

	vector<int> cols;
	for (int j = 0; j < arr[row].size(); j++)
		if (arr[row][j] == 1)
			cols.push_back(j);

	for (int i = 0; i < cols.size(); i++)
	{
		cov.resize(h);
		cov[h - 1] = cName[cols[i]];
		findCov(arr, rc, cc, cName, cols[i], h + 1, cov, res);
	}
}