#include <bits/stdc++.h>

using namespace std;

bool check(const string &s, int m) {
  string target = "yuki";
  int p = 0;
  for (int i = 0; i < target.length(); i++) {
    int pass = 0;
    for (int j = 0; j < m; j++) {
      if (p >= s.length() || s[p] < target[i]) return false;
      if (s[p] > target[i]) ++pass;
      ++p;
    }
    m -= pass;
  }
  return s.length() - p >= m;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  string s;
  cin >> n >> s;

  sort(s.begin(), s.end());
  reverse(s.begin(), s.end());

  int ub = n + 1;
  int lb = 0;

  while (ub - lb > 1) {
    int mi = (lb + ub) / 2;
    if (check(s, mi))
      lb = mi;
    else
      ub = mi;
  }

  cout << lb << endl;
  
  return 0;
}