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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.io.BufferedReader
import java.io.IOException
import java.io.InputStreamReader
import java.io.PrintWriter
import java.util.*

private fun solve() {
    val n = nextInt()
    val s = next()
    var res = 0
    for (i in 0 until n) {
        if (s[i] != 'A') {
            continue
        }
        if (i + 2 < n && s[i + 1] == 'B' && s[i + 2] == 'C') {
            ++res
        }
    }
    println(res)
}

fun main(args: Array<String>) {
    solve()
    out.close()
}

private var br = BufferedReader(InputStreamReader(System.`in`))
private var st: StringTokenizer? = null
private var out = PrintWriter(System.out)

@Throws(IOException::class)
private fun next(): String {
    while (st == null || !st!!.hasMoreTokens()) {
        st = StringTokenizer(br.readLine())
    }
    return st!!.nextToken()
}

@Throws(IOException::class)
private fun nextInt(): Int {
    return next().toInt()
}

@Throws(IOException::class)
private fun nextLong(): Long {
    return next().toLong()
}