#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
using ll=long long;
using ld=double;
ld pie=3.14159265359;
ll mod=998244353;
long long inf=100000000000000001;
int main(){
    ll n;
    cin >> n;
    string s;
    cin >> s;
    map<pair<char,ll>,ll>memo;
    for (ll i = 0; i < s.size(); i++)
    {
        memo[{s[i],i%3}]+=1;
    }
    ll ans=min(memo[{'c',0}],min(memo[{'o',1}],memo[{'n',2}]));
    ans+=min(memo[{'c',1}],min(memo[{'o',2}],memo[{'n',0}]));
    ans+=min(memo[{'c',2}],min(memo[{'o',0}],memo[{'n',1}]));
    cout << ans << endl;
}