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)

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
/**
*   author: j o s e m a g o
*   user: m a m i s a k i
**/
using namespace std;

/***PLANTILLA***/

using namespace __gnu_pbds; //*st.find_by_order(1);  st.order_of_key(p);
#pragma GCC optimize ("Ofast")
#define mp make_pair
#define lb lower_bound
#define ub upper_bound
#define all(v) (v).begin(),(v).end()
#define mset(a,v) memset(a,v,sizeof(a))
#define pb push_back
#define sz(x) ((int)(x).size())
#define rsz resize
#define ln "\n"
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;
typedef double dbl;
typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
const ld PI = 2*acos(0.0);
const int MOD = 1000000007;

string tostring(auto a){
    stringstream ss;ss<<a;string s = ss.str();
    return s;
}

/**Mi Debug**/
#define var(x) cout<<#x<<" = ";
#define db(x) cout<<#x<<" = "<<x<<"\n";
void dbvector(vector<auto>&v){
    int c = -1;
    for(auto i: v){
        c++;cout<<"["<<c<<":"<<i<<"] ";
    }cout<<"\n";
}
void dbmapa(map<auto,auto>mp){
   for(auto x : mp) cout<<"{"<<x.first<<":"<<x.second<<"} ";cout<<"\n";
}
void dbstring(string v){
    int c = -1;
    for(auto i: v){
        c++;cout<<"["<<c<<":"<<i<<"] ";
    }cout<<"\n";
}

/***********Code***************/

const int JJJ = 100100;










int main(){

  //freopen("input.in","r",stdin);
  //freopen("input.out","w",stdout);

    ios_base::sync_with_stdio(0); cin.tie(0);

    int n;
    cin >> n;
    string s;
    cin >> s;
    int i = 0;
    int cont = 0;
    for(;i < n;){
        if(s[i] == 'A' && s[i+1] == 'B' && s[i+2] == 'C'){
            cont++;
            i+=3;
        }
        else{
            i++;
        }
    }

    cout<<cont<<"\n";




    return 0;
}