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
def max_divisible_numbers(s):
    n = len(s)

    # Create a DP table to store the maximum number of divisible-by-3 numbers for each prefix
    dp = [[0] * 3 for _ in range(n + 1)]

    for i in range(1, n + 1):
        # Calculate the remainder of the current digit when divided by 3
        remainder = int(s[i - 1]) % 3

        # Update the DP table based on the remainder and the previous state
        dp[i][0] = dp[i - 1][0] + (remainder == 0)
        dp[i][1] = max(dp[i - 1][1] + (remainder == 1), dp[i - 1][0] + (remainder == 2))
        dp[i][2] = max(dp[i - 1][2] + (remainder == 2), dp[i - 1][0] + (remainder == 1))

    # Return the maximum number of divisible-by-3 numbers for the entire string
    return dp[n][0]

# Read the input number and call the function
s = input().strip()
result = max_divisible_numbers(s)
print(result)