#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]++;
        }
    }

    int64_t ans = 0;
    set<int64_t> st;
    for (int64_t i = 0; i < 3; i++) {
        const int64_t add = min({ c_num[i], o_num[(i + 1) % 3], n_num[(i + 2) % 3] });
        if (add == 0) {
            continue;
        }
        ans += add;
        st.insert(i);
    }

    const int64_t waste = N - ans;
    const int64_t sub = max((int64_t)(st.size() - 1) - waste, (int64_t)0);

    cout << ans - sub << endl;
}