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++14 (GCC 5.4.1) (judge verdict: Accepted)

//Count ABC
#include <bits/stdc++.h> //C++の機能を「全て」読み込むための命令
#define rep(i,n) for(int i=0; i<(n); ++i)
#define cout(x) cout<<(x)<<endl
using namespace std;
using ll = long long;
using P = pair<int,int>;
const ll inf=1e18;
const int N=2e5+10;
ll factorial(ll x){//階乗の計算
    if(x==0||x==1) return 1;
    return x*factorial(x-1);
}
ll gcd(ll a ,ll b){return b ? gcd(b,a%b) : a;}//最大公約数
ll lcm(ll a, ll b){return a/gcd(a,b)*b;}//最小公倍数
int num_digit(ll a){//桁数を求める
    int num_dig = 0;
    while(a!=0){
        a /= 10;
        ++num_dig;
    }
    return num_dig;
}
vector<ll> digit(ll a){//桁の数字を求める
    vector<ll> dig(num_digit(a));
    for(int i=num_digit(a)-1; i>=0; --i){
        dig[i] = a%10;
        a /= 10; 
    }
    return dig;
}


int main(){
    int n;
    cin >> n;
    string s;
    cin >> s;

    int cnt=0;
    for(int i=0;i<=n-3;++i){
        if(s.substr(i,3)=="ABC") ++cnt;
    }
    cout(cnt);
    return 0;
}