#include <iostream>
#include <vector>
#include <string>
using namespace std;

int main(){
    int N;
    cin >> N;
    string S;
    cin >> S;
    vector<vector<int>> cnt(3, vector<int>(3, 0));
    for (int i = 0; i < 3 * N; i++){
        if (S[i] == 'c') cnt[0][i % 3]++;
        else if (S[i] == 'o') cnt[1][i % 3]++;
        else if (S[i] == 'n') cnt[2][i % 3]++;
    }
    vector<int> min_sum(3);
    int ans = 0;
    for (int i = 0; i < 3; i++){
        min_sum[i] = min(cnt[0][i], min(cnt[1][(i + 1) % 3], cnt[2][(i + 2) % 3]));
        ans += min_sum[i];
    }
    if (ans == N){
        if (min_sum[0] == N) cout << N << endl;
        else cout << N - 1 << endl;
    }
    else{
        cout << ans << endl;
    }
}