#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

int main(){
    ll n;
    cin >> n;

    string s;
    cin >> s;

    vector<vector<ll>> cnt(3, vector<ll>(3, 0));
    rep(i, 3*n){
        if(s[i]=='c') cnt[i%3][0]++;
        if(s[i]=='o') cnt[i%3][1]++;
        if(s[i]=='n') cnt[i%3][2]++;
    }

    ll ans = 0;
    ll rest = n;
    //con
    ans += min(cnt[0][0], min(cnt[1][1], cnt[2][2]));
    //onc
    ll x = min(cnt[0][1], min(cnt[1][2], cnt[2][0]));
    //nco
    ll y = min(cnt[0][2], min(cnt[1][0], cnt[2][1]));
    ans += min(x+y, rest-1);

    cout << ans << endl;
}