# your code goes here
from itertools import permutations 
t = int(input())
l = []
ans = []
for i in range(t):
	s = input()
	l.append(s)
res = list(permutations(l))	
for x in res:
	i = 0
	j = i+1
	c = 0
	for k in range(len(x)):
		if j < len(x):
			first_set = set(x[i])
			second_set = set(x[j])
			overlap = first_set.intersection(second_set)
			c += len(overlap)
			# print(x[i],x[j],c)
			i += 1
			j += 1 
	ans.append(c)		
print(min(ans))		
 

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