#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define fix(x) fixed << setprecision(x)
#define asc(x) x, vector<x>, greater<x>
#define rep(i, n) for(ll i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    string s, t = "con";
    cin >> n >> s;
    vector<vector<int>> cnt(3,vector<int>(3,0));
    rep(i,n*3){
        rep(j,3){
            if(s[i]==t[j]) cnt[i%3][j]++;
        }
    }
    vector<int> ans(3,1001001);
    rep(i,3){
        rep(j,3){
            chmin(ans[i], cnt[(i+j)%3][j]);
        }
    }
    if(ans[0]==n){
        cout << n << '\n';
    }else{
        cout << min(ans[0]+ans[1]+ans[2], n-1) << '\n';
    }
    return 0;
}