#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[8]={-1,0,1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
string xxx="yuki";
bool large(string t){
  if(t.size()==0)return false;
  rep(i,4){
    if(xxx[i]<t[i])return true;
    else if(xxx[i]>t[i])return false;
  }
  return t.size()>4;
}
int main(){
  ll n;cin >> n;
  string s;cin >> s;sort(all(s));rev(all(s));
  ll ok=0,ng=n+1;
  while(ng-ok>1){
    ll mid=(ok+ng)/2;
    vector<string> g(mid);
    ll now=0;
    ll comp=0;
    while(true){
      for(int i=comp;i<mid;i++){
        g[i]+=s[now];now++;
        if(large(g[i]))comp++;
        if(now>=n)break;
      }
      if(now>=n||comp>=mid)break;
    }
    //cout << mid <<endl;
    //rep(i,mid)cout << g[i] <<endl;
    if(comp==mid)ok=mid;
    else ng=mid;
  }
  cout << ok <<endl;
}