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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Linq;

namespace AtCoder_practice0801
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            string S = Console.ReadLine();

            Console.WriteLine(CountOf(S, "ABC"));

        }

        public static int CountOf(string target, params string[] strArray)
        {
            int count = 0;

            foreach (string str in strArray)
            {
                int index = target.IndexOf(str, 0);
                while (index != -1)
                {
                    count++;
                    index = target.IndexOf(str, index + str.Length);
                }
            }

            return count;
        }
    }
}