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

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n; cin >> n;
    string s; cin >> s;
    vector<vector<int>> cnt(3, vector<int>(3));
    string sub = "con";
    for (int i = 0; i < 3 * n; i++) {
        for (int j = 0; j < 3; j++) {
            if (s[i] == sub[j]) {
                cnt[(i + 3 - j) % 3][j]++;
            }
        }
    }
    int ans = 0, msk;
    for (int i = 0; i < 3; i++) {
        int x = *min_element(cnt[i].begin(), cnt[i].end());
        if (x > 0) {
            ans += x;
            msk ^= (1 << i);
        }
    }
    cout << min(ans, n - (__builtin_popcount(msk) > 1));
}