#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <set>
#include <random>
#include <iomanip>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)

template<class T>
using vi = vector<T>;

template<class T>
using vii = vector<vi<T>>;

template<class T>
using viii = vector<vii<T>>;


struct unionfind {
    vector<int> d;
    vector<int> cnt;
    unionfind(int n = 0) : cnt(n) {
        d = vector<int>(n, -1);
    }

    int find(int x) {
        if (d[x] < 0) return x;
        return d[x] = find(d[x]);
    }

    bool unite(int x, int y) {
        int rx = find(x);
        int ry = find(y);
        if (rx == ry) {
            cnt[rx]++;
            return false;
        }
        if (d[rx] > d[ry]) swap(rx, ry);
        d[rx] += d[ry];
        d[ry] = rx;
        cnt[rx] = max(cnt[rx], cnt[ry]) + 1;
        return true;
    }

    bool same(int x, int y) { return find(x) == find(y); }

    int size(int x) { return -d[find(x)]; }
};



int main()
{
    int n;
    string s;
    cin >> n >> s;
    vi<map<char, int>> d(3);
    rep(i, 3 * n) d[i % 3][s[i]]++;

    string con = "con";
    int ans = 0;
    vi<int> p = { 0, 1, 2 };
    do {
        int pos = 0;
        int ta = 0;
        rep(i, 3) {
            while (pos % 3 != p[i]) pos++;
            if (pos >= 3 * n) break;
            int temp = n;
            rep(j, 3) {
                int idx = (p[i] + j) % 3;
                temp = min(temp, d[idx][con[j]]);
            }
            ta += min((3 * n - pos) / 3, temp);
            pos += min((3 * n - pos) / 3, temp) * 3;
        }        
        ans = max(ans, ta);
    } while (next_permutation(p.begin(), p.end()));

    cout << ans << endl;
    return 0;
}