#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	string s; cin >> s;
	vector<vector<int>> data(3, vector<int>(3));
	rep(i, 3 * n) {
		if ('c' == s[i])data[i % 3][0]++;
		if ('o' == s[i])data[i % 3][1]++;
		if ('n' == s[i])data[i % 3][2]++;
	}
	int ans = 0;
	vector<int>v(3, INF);
	rep(i, 3) {
		rep(j, 3)chmin(v[i], data[j][(i + j) % 3]);
		ans += v[i];
	}
	if ((n == ans) &&(n != v[0]))ans--;
	cout << ans << endl;
	return 0;
}