file = open('18B.txt')
n = int(file.readline())
d = [0] * 10
for i in range(n):
    x = int(file.readline())
    for j in range(len(str(x))):
        d[int(str(x)[j])] += 1
ans = 10**10
for i in range(10):
    if d[i] != 0:
        ans = min(ans, d[i])
print(ans)