#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for (int i = 0; i < n; i++)
#define rrep(i,n) for (int i = n - 1; i >= 0; i--)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}

int n, C[3], O[3], N[3];
string s;

int main(){
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    cin >> n >> s;
    rep(i, 3 * n){
        if (s[i] == 'c'){
            C[i % 3]++;
        } else if (s[i] == 'o'){
            O[i % 3]++;
        } else if (s[i] == 'n'){
            N[i % 3]++;
        }
    }
    int l = 0, ans = 0;
    while (l + 2 < 3 * n){
        if (C[l % 3] > 0 && O[(l + 1) % 3] > 0 && N[(l + 2) % 3] > 0){
            C[l % 3]--;
            O[(l + 1) % 3]--;
            N[(l + 2) % 3]--;
            ans++;
            l += 3;
        } else{
            l++;
        }
    }
    cout << ans << "\n";
}