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>
using namespace std;
const int mod=998244353;
const int mex=2005;
#define ll long long 
#define test int t;cin>>t;while(t--)
#define fast  ios_base::sync_with_stdio(false);cin.tie(NULL);
#define fo(i,a,n) for(int i=a;i<n;i++)
#define rfo(i,a,b) for(int i=a;i>=b;i--)
#define bg begin()
#define en end()
#define fi first
#define se second
#define ub upper_bound
#define lb lower_bound
#define pb push_back
#define veci vector<int>
#define veclli vector<long long int> 
#define all(x) x.begin(),x.end()
#define sci(x) scanf("%d",&x);
#define scc(x) scanf("%c",&x);
#define scs(x) scanf("%s",x);
#define debug(arr,n) for(int i=0;i<n;i++) printf("%d ",arr[i]);
#define sz(x) x.size()
#define loop(x) for(auto it=x.begin();it!= x.end();it++) 
int main()
{
   int n;
   cin>>n;
   string s;
   cin>>s;
   int cnt=0;
   fo(i,0,n-2)
   {
       if(s[i]=='A'&&s[i+1]=='B'&&s[i+2]=='C') cnt++;
   }
   cout<<cnt;
}