문제 링크 https://www.acmicpc.net/problem/1316
import sys
n = int(input())
for i in range(n):
a = sys.stdin.readline().rstrip()
b = [a[0]]
for i in list(a):
if b[-1] == i:
b.append(i)
continue
elif i in b:
n -= 1
break
b.append(i)
print(n)