#include <iostream>
#include <algorithm>
using namespace std;
int n;
int tbl[26];
bool canmake(){
  const string yuki = "yuki";  
  int idx = 0;
  while(true){
    if(idx>=4 || tbl[yuki[idx]-'a']==0) break;
    tbl[yuki[idx]-'a']--;
    ++idx;
  }
  for(int j=(idx<4)?(yuki[idx]-'a'):0; j<26;++j){
    if(tbl[j]){
      tbl[j]--;
      return true;
    }
  }
  return false;
}

int main(){
  int cnt = 0;
  string s;
  cin >> n >> s;
  for(int i=0;i<n;++i) tbl[s[i]-'a']++;
  while(canmake()) ++cnt;
  cout <<cnt<<endl;
  return 0;
}