#include <iostream>
using namespace std;
int dta[9];// z y x~v u t~l k j i h~a
int main(){
  char yuki[4] = {'y','u','k','i'};
  int n;cin>>n;
  string s;cin>>s;
  for(int i = 0; s.size() > i; i++){
    int ok = false;
    for(int j = 0; 8 > j; j+=2){
      if(s[i] > yuki[j/2]){
        ok = true;
        dta[j]++;
        break;
      }else if(s[i] == yuki[j/2]){
        ok = true;
        dta[j+1]++;
        break;
      }
    }
    if(!ok){
      dta[8]++;
    }
  }
  int tans = (dta[7]>dta[8]?dta[8]+(dta[7]-dta[8])/2:dta[7]);
  for(int i = 5; 0 <= i; i-=2){
    int ans = min(dta[i],dta[i+1]);
    //cout << i << " " << i+1 << ":" << dta[i] << " " << dta[i+1] << endl;
    if(dta[i] > dta[i+1]){
      dta[i] -= dta[i+1];
      ans += min(dta[i],tans);
      if(dta[i] > tans){
        dta[i]-= tans;
        ans += dta[i]/=2;
      }
    }
    tans = ans;
  }
  cout << tans + dta[0] << endl;

}