#include <iostream>
#include <string>

using namespace std;

int main() {
    int n;
    string dna;

    cin >> n >> dna;

    int count = 0;
    for (int i = 0; i < n - 2; i++) {
        if (dna[i] == 'A' && dna[i + 1] == 'G' && dna[i + 2] == 'T') {
            count++;
        }
    }

    cout << count << endl;

    return 0;
}