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 Go (1.6) (judge verdict: Accepted)

package main
 
import (
	"fmt"
	"regexp"
)
 
func main() {
	var wordCount int
    var abcTestStr string
	fmt.Scanf("%d", &wordCount)
	fmt.Scanf("%s", &abcTestStr)

	var sLength = len([]byte(abcTestStr))
	if(sLength < 3 || 50 < sLength) {
        panic("allow length 1 to 50")
    }
	if(sLength != wordCount) {
        panic("allow length wordCount")
    }
	upperCaseAtoZRep := regexp.MustCompile(`^[A-Z]*`)
	if(!upperCaseAtoZRep.MatchString(abcTestStr)) {
		panic("allow AtoZ only")
	}
    splitAtoZRep := regexp.MustCompile(`ABC`)
    result := splitAtoZRep.FindAllStringSubmatch(abcTestStr, -1)  
	fmt.Printf("%d", len(result))
}