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

int A[3];

int main() {
    int N;
    string S;
    cin >> N >> S;
    int ans = 0;
    for (int i = 0; i < 3*N; i++) {
        if (i%3 == 0) {
            if (S[i] == 'c') A[0]++;
        } else if (i%3 == 1) {
            if (S[i] == 'o') A[1]++;
        } else {
            if (S[i] == 'n') A[2]++;
        }
    }
    int ans1 = min(A[0], min(A[1], A[2]));
    ans += ans1;
    for (int i = 0; i < 3; i++) A[i] = 0;
    
    for (int i = 0; i < 3*N; i++) {
        if (i%3 == 0) {
            if (S[i] == 'n') A[0]++;
        } else if (i%3 == 1) {
            if (S[i] == 'c') A[1]++;
        } else {
            if (S[i] == 'o') A[2]++;
        }
    }
    int ans2 = min(A[0], min(A[1], A[2]));
    ans += ans2;
    for (int i = 0; i < 3; i++) A[i] = 0;
    
    for (int i = 0; i < 3*N; i++) {
        if (i%3 == 0) {
            if (S[i] == 'o') A[0]++;
        } else if (i%3 == 1) {
            if (S[i] == 'n') A[1]++;
        } else {
            if (S[i] == 'c') A[2]++;
        }
    }
    int ans3 = min(A[0], min(A[1], A[2]));
    ans += ans3;

    if (ans2 > 0 && ans3 > 0) ans -= max(0, 2 - (N-ans));
    else if (ans2 > 0 || ans3 > 0) ans -= max(0, 1 - (N-ans));

    cout << ans << endl;
}