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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main(void){
    int n,i,k,count;
    char c;
    scanf("%d",&n);
    getchar();
    k=count=0;
    for(i=0;i<n;i++){
        c=getchar();
        if(c=='A'&&k==0)
            k++;
        else if(c=='B'&&k==1)
            k++;
        else if(c=='C'&&k==2)
            k++;
        else if(c=='A'&&k==1)
            k=1;
        else
            k=0;
        if(k==3){
            count++;
            k=0;
        }
        
    }
    printf("%d",count);
    return 0;
}