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

#ifdef _RUTHEN
#include <debug.hpp>
#else
#define show(...) true
#endif

using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
template <class T> using V = vector<T>;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N;
    cin >> N;
    string S;
    cin >> S;
    bool ok = true;
    rep(i, 3 * N) {
        if (i % 3 == 0 and S[i] != 'c') ok = false;
        if (i % 3 == 1 and S[i] != 'o') ok = false;
        if (i % 3 == 2 and S[i] != 'n') ok = false;
    }
    if (ok) {
        cout << N << '\n';
        return 0;
    }
    V<V<int>> cnt(3, V<int>(26));
    rep(i, 3 * N) cnt[i % 3][S[i] - 'a']++;
    int ans = 0;
    rep(i, 3) ans += min({cnt[(i + 0) % 3]['c' - 'a'], cnt[(i + 1) % 3]['o' - 'a'], cnt[(i + 2) % 3]['n' - 'a']});
    ans = min(ans, N - 1);
    cout << ans << '\n';
    return 0;
}