#include <iostream>
using namespace std;

int d[3][3];

int main()
{
    int n;
    string s;
    cin >> n >> s;
    for (int i = 0; i < n * 3; i++)
    {
        if (s[i] == 'c')
        {
            d[i % 3][0]++;
        }
        if (s[i] == 'o')
        {
            d[i % 3][1]++;
        }
        if (s[i] == 'n')
        {
            d[i % 3][2]++;
        }
    }
    int e[3] = {n, n, n};
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            e[i] = min(e[i], d[(i + j) % 3][j]);
        }
    }
    int ans = e[0] + e[1] + e[2];
    if (ans == n)
    {
        if (e[0] < n)
        {
            ans--;
        }
    }
    cout << ans << endl;
}