#include <stdio.h>
#define KODOKSZAMA 999
#define KODHOSSZ 6

int min_put_c = -1;

int min_put(int n)
{
	if (n == -1)
		return min_put_c;
	if (min_put_c == -1)
		return min_put_c = n;
	if (n < min_put_c)
		return min_put_c = n;
	return min_put_c;
}

int hammingtav(char a[], char b[])
{
	int tav = 0;
	int i;
	for (i = 0; i <= KODHOSSZ; i++)
		if (a[i] != b[i])
			tav++;
	return tav;
}



int main (int argc, char *argv[])
{
	int i = 0; /* sor indexe */
	int j = 0; /* karakterhelyindex */
	int t; /* puffer */

	char kodok[KODOKSZAMA][KODHOSSZ+1]; /* a kodok */

	while(1) {
		t = getchar();
		if (t ==  -1) /*EOF)*/
			break;
		if (t == '\n') {
			kodok[i][j] = '\0';
			i++;
			j = 0;
			continue;
		}
		kodok[i][j++] = t;
	}
	if (j > 0)
		i++;
	while (--i >= 0) {
		j = i;
		while (--j >= 0) {
			min_put(hammingtav(kodok[i], kodok[j]));
		}
	}
	printf ("%d\n", min_put(-1));
	return 0;
}