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
s = input()
a = [int(s[i]) for i in range(len(s))]
for i in range(len(a)):
    a[i] = a[i] % 3
count = 0
pred = set()
i = 0
while i <= len(a) - 1:
    if a[i] == 0:
        count += 1
        pred = set()
    elif a[i] == 1 and (2 in pred):
        count += 1
        pred = set()
    elif a[i] == 1:
        if 1 in pred:
            pred.add(2)
        else:
            pred.add(1)
    elif a[i] == 2 and (1 in pred):
        count += 1
        pred = set()
    else:
        if 2 in pred:
            pred.add(1)
        else:
            pred.add(2)
    i += 1
print(count)

    
    
    

            
        
        