#include <bits/stdc++.h>
using namespace std;
int f(vector<vector<int>>& freq, int k) {
    int res = 1<<30;
    for( int i = 0; i < 3; i++ ) {
        res = min(res, freq[(k+i)%3][i]);
    }
    return res;
}
int main() {
    int N;
    string s;
    cin >> N >> s;
    vector<vector<int>> freq(3, vector<int>(3));
    for( int i = 0; i < 3*N; i++ ) {
        char c = s[i];
        if( c == 'c' ) freq[i%3][0]++;
        else if( c == 'o' ) freq[i%3][1]++;
        else if( c == 'n' ) freq[i%3][2]++;
    }
    int len = 0, ans = 0;
    for( int i = 0; i < 3; i++ ) {
        int k = f(freq, i);
        if( len+3*k <= 3*N ) {
            ans += k;
            len += 3*k+1;
        }else {
            ans += (3*N-len)/3;
            cout << ans << endl;
            return 0;
        }
    }
    cout << ans << endl;
}