#include <bits/stdc++.h>

using namespace std;

#define rep(i,n) for(int i = 0; i < (int)(n); ++i)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; --i)
#define ALL(a) a.begin(), a.end()
#define Sort(a) sort(a.begin(), a.end())
#define RSort(a) sort(a.rbegin(), a.rend())

typedef long long int ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef vector<char> vc;
typedef vector<string> vst;
typedef vector<double> vd;
typedef pair<long long, long long> P;

const long long INF = 0x1fffffffffffffff;
const long long MOD = 1000000007;
const long double PI = acos(-1);
 
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T, class U> inline T vin(T& vec, U n) { vec.resize(n); for(int i = 0; i < (int) n; ++i) cin >> vec[i]; return vec; }
template<class T> inline void vout(T vec, string s = "\n"){ for(auto x : vec) cout << x << s; }
template<class... T> void in(T&... a){ (cin >> ... >> a); }
void out(){ cout << '\n'; }
template<class T, class... Ts> void out(const T& a, const Ts&... b){ cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; }
template<class T, class U> void inGraph(vector<vector<T>>& G, U n, U m, bool directed = false){ G.resize(n); for(int i = 0; i < m; i++){ int a, b; cin >> a >> b; a--, b--; G[a].push_back(b); if(!directed) G[b].push_back(a); } }

ll n;
string s;

void input(){
    in(n, s);
}
 
void solve(){
    vector<vector<ll>> cnt(3, vector<ll>(3));
    rep(i, 3 * n){
        if(s[i] == 'c'){
            cnt[0][i % 3]++;
        }
        if(s[i] == 'o'){
            cnt[1][i % 3]++;
        }
        if(s[i] == 'n'){
            cnt[2][i % 3]++;
        }
    }
    ll m = 3 * n;
    ll ans = 0;
    ll a = min({cnt[0][0], cnt[1][1], cnt[2][2]}), b = min({cnt[0][1], cnt[1][2], cnt[2][0]}), c = min({cnt[0][2], cnt[1][0], cnt[2][1]});
    ans += a; m -= 3 * a;
    b = min(b, (m - 1) / 3);
    ans += b; m -= b * 3;
    c = min(c, (m - 2) / 3);
    ans += c;
    out(ans);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    input();
    solve();
}