Polycarp likes numbers that are divisible by 3.

He has a huge number $s$. Polycarp wants to cut from it the maximum number of numbers that are divisible by $3$. To do this, he makes an arbitrary number of vertical cuts between pairs of adjacent digits. As a result, after $m$ such cuts, there will be $m+1$ parts in total. Polycarp analyzes each of the obtained numbers and finds the number of those that are divisible by $3$.

For example, if the original number is $s=3121$, then Polycarp can cut it into three parts with two cuts: $3|1|21$. As a result, he will get two numbers that are divisible by $3$.

Polycarp can make an arbitrary number of vertical cuts, where each cut is made between a pair of adjacent digits. The resulting numbers cannot contain extra leading zeroes (that is, the number can begin with 0 if and only if this number is exactly one character '0'). For example, 007, 01 and 00099 are not valid numbers, but 90, 0 and 10001 are valid.

What is the maximum number of numbers divisible by $3$ that Polycarp can obtain?
The first line of the input contains a positive integer $s$. The number of digits of the number $s$ is between $1$ and $2\cdot10^5$, inclusive. The first (leftmost) digit is not equal to 0.
3121
2
6
1
1000000000000000000000000000000000
33
201920181
4
4
0
10
1
11
0
12
1
13
1
31
1
14139582796
6
1670000
5
604500
5
40041
2
10000170
5
import itertools
import math
import time
from builtins import input
from math import gcd as gcd
import sys
import queue
import itertools
import collections
from heapq import heappop, heappush
import random
import os
from random import randint
import decimal

# from sys import stdin, stdout
# input, print = stdin.readline, stdout.write

decimal.getcontext().prec = 18


def solve():
    s = str(input())

    last = ""
    res = 0

    for i in range(len(s)):
        last += s[i]
        cur = ""
        for j in range(len(last) - 1, -1, -1):
            cur += last[j]
            if int(cur) % 3 == 0:
                res += 1
                last = ""
                break

    print(res)


if __name__ == '__main__':
    multi_test = 0

    if multi_test == 1:
        t = int(sys.stdin.readline())
        for _ in range(t):
            solve()
    else:
        solve()
