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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::Read;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();

    let answer = solve(&buf);

    println!("{}", answer);
}

fn solve(input: &str) -> String {
    let mut iterator = input.split_whitespace();

    iterator.next();
    let s = iterator.next().unwrap();
    let vec: Vec<_> = s.match_indices("ABC").collect();

    return vec.len().to_string();
}

#[test]
fn test() {
    assert_eq!(
        solve(
            r"10
ZABCDBABCQ"
        ),
        "2"
    );
    assert_eq!(
        solve(
            r"19
THREEONEFOURONEFIVE"
        ),
        "0"
    );
    assert_eq!(
        solve(
            r"33
ABCCABCBABCCABACBCBBABCBCBCBCABCB"
        ),
        "5"
    );
}