#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int n;
  string s;
  cin>>n>>s;
  vector<Int> cnt(26,0);
  for(char c:s) cnt[c-'a']++;

  auto check=
    [&](Int x)->Int{
      x-=cnt[25];
      if(x<=0) return 1;
      
      if(cnt[24]<x) return 0;
      Int a=cnt[24]-x;
      for(Int i='u'-'a'+1;i<'y'-'a';i++) a+=cnt[i];      
      x-=a;      
      if(x<=0) return 1;
      
      if(cnt[20]<x) return 0;
      Int b=cnt[20]-x;
      for(Int i='k'-'a'+1;i<'u'-'a';i++) b+=cnt[i];
      x-=b;
      if(x<=0) return 1;
      
      if(cnt[10]<x) return 0;      
      Int c=cnt[10]-x;
      for(Int i='i'-'a'+1;i<'k'-'a';i++) c+=cnt[i];
      x-=c;
      if(x<=0) return 1;
      
      if(cnt[8]<x) return 0;   
      Int d=cnt[8]-x;
      for(Int i='a'-'a'+0;i<'i'-'a';i++) d+=cnt[i];      
      x-=d;
      return x<=0;
    };
  
  Int l=0,r=n+1;
  while(l+1<r){
    Int m=(l+r)>>1;
    if(check(m)) l=m;
    else r=m;
  }
  cout<<l<<endl;
  return 0;
}