#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]++;
        }
    }
    ans += min(A[0], min(A[1], A[2]));
    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]++;
        }
    }
    ans += min(min(N-1, A[0]), min(A[1], A[2]));
    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]++;
        }
    }
    ans += min(min(N-1, A[0]), min(A[1], A[2]));

    cout << ans << endl;
}