#include <cstdio>
#include <algorithm>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <string>
#include <string.h>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <map>
#include <set>
#include <iostream>
#include <sstream>
#include <numeric>
#include <cctype>
#include <bitset>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define gep(i,g,j) for(int i = g.head[j]; i != -1; i = g.e[i].next)
#define each(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define rng(a) a.begin(),a.end()
#define maxs(x,y) x = max(x,y)
#define mins(x,y) x = min(x,y)
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcount
#define snuke srand((unsigned)clock()+(unsigned)time(NULL));
#define df(x) int x = in()
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
inline int in() { int x; scanf("%d",&x); return x;}
inline void priv(vi a) { rep(i,sz(a)) printf("%d%c",a[i],i==sz(a)-1?'\n':' ');}

const int MX = 100005, INF = 1001001001;
const ll LINF = 1e18;
const double eps = 1e-10;

const string t = "yuki$";

bool f(string s, int x) {
  if (x == 0) return true;
  int i = sz(s)-1;
  rep(ti,5) {
    while (i >= 0 && s[i] > t[ti]) {
      --x;
      if (x == 0) return true;
      --i;
    }
    int y = 0;
    while (i >= 0 && s[i] == t[ti]) {
      if (y < x) {
        y++;
      } else {
        --x;
        --y;
        if (x == 0) return true;
      }
      --i;
    }
    if (y < x) return false;
  }
  return false;
}

int main() {
  int n;
  string s;
  cin >> n >> s;
  sort(rng(s));
  int l = 0, r = n+1, c;
  while (l+1<r) {
    c = (l+r)>>1;
    if (f(s,c)) l = c; else r = c;
  }
  cout<<l<<endl;
  return 0;
}