#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001



int main(){
	
	int N;
	cin>>N;
	
	string S;
	cin>>S;
	
	rep(i,N*3){
		rep(j,i%3){
			if(S[i]=='c')S[i] = 'n';
			else if(S[i]=='o')S[i] = 'c';
			else if(S[i]=='n') S[i] = 'o';
		}
	}
	int ans = 0;
	rep(i,3){
		char c = 'c';
		if(i==1)c = 'o';
		if(i==2)c = 'n';
		map<int,int> mp;
		rep(j,N*3){
			if(S[j]==c)mp[j%3]++;
		}
		ans += min({mp[0],mp[1],mp[2]});
	}
	cout<<ans<<endl;
	return 0;
}