N = input()
dic = {}
for i in range(10):
dic[i] = 0
for i in N:
dic[int(i)] += 1
if (dic[6] + dic[9]) % 2 == 0:
dic[6] = (dic[6] + dic[9]) //2
else:
dic[6] = (dic[6] + dic[9]) //2 + 1
max = 0
for i in range(9):
if dic[i] > max:
max = dic[i]
print(max)