#include <stdio.h>
#include <string.h>

char radky[2000][7];

int min = -1;
int total = 0;

void printit()
{
	printf("The highest possible quality is 1/%i.\n", min);
}

void vyresto()
{
	int radek,sloupec, _radek;
	int _min;
	int higher;
	
	higher = 0;
	for (radek = 0; radek < total; radek++)
	{
	_min = 0;
	for(_radek = 0; _radek < total; _radek++)
	{
		for (sloupec = 0; sloupec < 7; sloupec++)
		{
			if (radky[radek][sloupec] != radky[_radek][sloupec]) {
	/*		printf("radky:%i,_%i\n", radek, _radek);*/
				_min++;
			}
/*			if ((min != -1) && (_min > min))
			{
				higher = 1;
				break;
			}*/
		}
	}
	if ((min == -1) || (min > _min)) min = _min;
	}
}

int main()
{
	int i,k;
	char buffer[8] = "\0";

	for (;;){
		gets(buffer);

		sscanf(buffer, "%i", &total);

		if (total == 0)
			return 0;

		for (i = 0; i < total; i++)
		{
			for (k = 0; k< 7; k++)
				radky[i][k] = getchar();

			getchar();
		}
		vyresto();
		printit();
		min = -1;
	} 

	return 0;
}