#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------


int C[256][3];
int N;
string S;

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>S;
	FOR(i,3*N) C[S[i]][i%3]++;
	
	int a=min({C['c'][0],C['o'][1],C['n'][2]});
	int b=min({C['c'][1],C['o'][2],C['n'][0]});
	int c=min({C['c'][2],C['o'][0],C['n'][1]});
	
	int ret=a+b+c;
	if(c&&a*3+2+b*3+c*3>3*N) ret--;
	if(c==0&&b&&a*3+1+b*3>3*N) ret--;
	
	
	cout<<ret<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}