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

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n; cin >> n;
    string sub = "con";
    vector<string> s(3);
    {
        string xd; cin >> xd;
        for (int i = 0; i < 3 * n; i++) {
            s[i % 3].push_back(xd[i]);
        }
    }
    int ans = 0;
    for (int i = 0; i < 3; i++) {
        int cnt = n;
        for (int j = 0; j < 3; j++) {
            cnt = min(cnt, (int)count_if(s[(i + j) % 3].begin(), s[(i + j) % 3].end(), [&](char u) {
                return u == sub[j];
            }));
            sort(s[(i + j) % 3].begin(), s[(i + j) % 3].end(), [&](char u, char v) {
                return (u == sub[j]) < (v == sub[j]);
            });
        }
        ans += cnt;
        while (cnt--) {
            for (int j = 0; j < 3; j++) {
                s[j].pop_back();
            }
        }
    }
    cout << ans;
}