#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i,n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
const long long INF = 1LL << 60;
const int MOD = 1000000007;
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool etmin(T& a, T b) { if (a < b) { a = b; return true; } return false; }
//https://www.creativ.xyz/dump-cpp-652/
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
 
// vector
template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec) is >> x;
    return is;
}
// pair
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}
// vector
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &vec) {
    os << "{";
    for (int i = 0; i < vec.size(); i++) {
        os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
    }
    os << "}";
    return os;
}
// map
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
    os << "{";
    repi(itr, map_var) {
        os << *itr;
        itr++;
        if (itr != map_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
// set
template <typename T>
ostream &operator<<(ostream &os, set<T> &set_var) {
    os << "{";
    repi(itr, set_var) {
        os << *itr;
        itr++;
        if (itr != set_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
 
#define DUMPOUT cerr
 
void dump_func() {
    DUMPOUT << endl;
}
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) {
        DUMPOUT << ", ";
    }
    dump_func(std::move(tail)...);
}

#ifdef DEBUG_
#define DEB
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
struct KMP{
    vector <int> table;
    string p;
    int sz;
    KMP(string S){ //探したいword, pattern
        sz = S.size();
        p = S;
        table.resize(sz+1);
        int j = table[0] = -1;
        for (int i = 0; i < S.size(); i++) {
            while (j >= 0 && S[i] != S[j]) j = table[j];
            j++;
            //table[i+1] = j;
            if (S[i+1] == S[j]) table[i+1] = table[j]; 
            else table[i+1] = j;
        }
        //rep(i, table.size()) cout<<table[i]<<endl;
    }
    vector <pair<int,int>> findfrom(string t) { //text
        int n = t.size();
        int count = 0; //数を調べるだけなら
        vector <pair<int,int>> data;
        for (int i = 0, k = 0; i < n; ++i) {
            while (k >= 0 && p[k] != t[i]) k = table[k];
            if (++k >= sz) {
                data.push_back({i-sz+1,i});
                k = table[k];
                count++;
            }
        }
        cout<<count<<endl; exit(0);
        return data; //0indexed 
    }
};
signed main(void) { cin.tie(0); ios::sync_with_stdio(false);
    int n; cin>>n;
    string s; cin>>s;
    KMP kmp("ABC");
    kmp.findfrom(s);
}

Measured memory_bytes: 256