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)

#define DEBUG 1
#include <bits/stdc++.h>
#define loop(n) for (lint ngtkana_is_a_genius = 0; ngtkana_is_a_genius < lint(n); ngtkana_is_a_genius++)
#define rep(i, begin, end) for (lint i = lint(begin); (i) < lint(end); i++)
#define all(v) v.begin(), v.end()
#define rand(l, r) std::uniform_int_distribution<>(l, r)(mt)
using lint = long long;
auto mt = std::mt19937_64(std::random_device{}());
auto cmn = [](auto&& a, auto b){ if (a > b) {a = b; return true;} return false; };
auto cmx = [](auto&& a, auto b){ if (a < b) {a = b; return true;} return false; };
void debug_impl() { std::cerr << std::endl; }
template <typename Head, typename... Tail>
void debug_impl(Head head, Tail... tail) { std::cerr << " " << head; debug_impl(tail...); }
#if DEBUG
#define debug(...)\
  do {\
    std::cerr << std::boolalpha << "[" << #__VA_ARGS__ << "]:";\
    debug_impl(__VA_ARGS__);\
    std::cerr << std::noboolalpha;\
  } while (false)
#else
#define debug(...) {}
#endif

int main() {
  std::cin.tie(0); std::cin.sync_with_stdio(false);
  int n; std::cin >> n;
  std::string s; std::cin >> s;
  int ans = 0;
  rep(i,0,n) {
    ans += s.substr(i,3) == "ABC";
  }
  std::cout << ans << std::endl;
  return 0;
}