#include <bits/stdc++.h>
using namespace std;

int main() {
    int64_t N;
    string S;
    cin >> N >> S;
    vector<int64_t> c_num(3, 0), o_num(3, 0), n_num(3, 0);
    for (int64_t i = 0; i < 3 * N; i++) {
        if (S[i] == 'c') {
            c_num[i % 3]++;
        } else if (S[i] == 'o') {
            o_num[i % 3]++;
        } else if (S[i] == 'n') {
            n_num[i % 3]++;
        }
    }

    vector<int64_t> vec(3);
    for (int64_t i = 0; i < 3; i++) {
        vec[i] = min({ c_num[i], o_num[(i + 1) % 3], n_num[(i + 2) % 3] });
    }

    const int64_t sum = vec[0] + vec[1] + vec[2];

    if (sum == N) {
        if (vec[0] == N) {
            cout << N << endl;
        } else {
            cout << N - 1 << endl;
        }
    } else {
        cout << min(sum, N - 1) << endl;
    }
}