Problem:
Score : 200 points

Problem Statement

We have a string S of length N consisting of uppercase English letters.

How many times does ABC occur in S as contiguous subsequences (see Sample Inputs and Outputs)?

Constraints

3 \leq N \leq 50

S consists of uppercase English letters.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print number of occurrences of ABC in S as contiguous subsequences.

Sample Input 1

10
ZABCDBABCQ

Sample Output 1

2

Two contiguous subsequences of S are equal to ABC: the 2-nd through 4-th characters, and the 7-th through 9-th characters.

Sample Input 2

19
THREEONEFOURONEFIVE

Sample Output 2

0

No contiguous subsequences of S are equal to ABC.

Sample Input 3

33
ABCCABCBABCCABACBCBBABCBCBCBCABCB

Sample Output 3

5

Solution in Python (3.4.3) (judge verdict: Accepted)

N = int(input())
S = input()
state = 0
ans = 0

def isABC(s):
    global state
    if state==0:
        if s=="A":
            state = 1
        return 0
    elif state==1:
        if s=="B":
            state = 2
        elif s=="A":
            state=1
        else:
            state=0
        return 0
    else:
        if s=="C":
            state=0
            return 1
        elif s=="A":
            state=1
            return 0
        else:
            state=0
            return 0

for i in S:
    ans += isABC(i)
print(ans)