#include <stdio.h>
#include <algorithm>
using namespace std;

int main(){
	int n;char s[100001];scanf("%d%s",&n,s);
	int ans=0,c[150]={};
	for(int i=0;i<n;i++){
		c[s[i]]++;
	}
	int cy=0,overu=0,cu=0,overk=0,ck=0,overi=0,ci=0,cc=0;
	for(char i='z';i>='a';i--){
		if(i>'y')ans+=c[i];
		else if(i=='y')cy+=c[i];
		else if(i>'u')overu+=c[i];
		else if(i=='u')cu+=c[i];
		else if(i>'k')overk+=c[i];
		else if(i=='k')ck+=c[i];
		else if(i>'i')overi+=c[i];
		else if(i=='i')ci+=c[i];
		else cc+=c[i];
	}
	//for(char i='z';i>='a';i--)if(c[i])printf("%d\n",c[i]);
	int m=min(cy,min(cu,min(ck,min(ci,cc))));
	ans+=m;cy-=m,cu-=m,ck-=m,ci-=m,cc-=m;
	m=min(cy,min(cu,min(ck,ci/2)));
	ans+=m;cy-=m,cu-=m,ck-=m,ci-=m;
	m=min(cy,min(cu,min(ck,overi)));
	ans+=m;cy-=m,cu-=m,ck-=m,overi-=m;
	m=min(cy,min(cu,ck/2));
	ans+=m;cy-=m,cu-=m,ck-=m;
	m=min(cy,min(cu,overk));
	ans+=m;cy-=m,cu-=m,overk-=m;
	m=min(cy,cu/2);
	ans+=m;cy-=m,cu-=m;
	m=min(cy,overu);
	ans+=m;cy-=m,overu-=m;
	m=cy/2;
	ans+=m;cy-=m;
	printf("%d\n",ans);
	
	return 0;
}