/* -*- coding: utf-8 -*-
 *
 * 145.cc: No.145 yukiover - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

const int Z = 'z' - 'a';
const int Y = 'y' - 'a';
const int U = 'u' - 'a';
const int K = 'k' - 'a';
const int I = 'i' - 'a';

/* typedef */

/* global variables */

int cs[26];

/* subroutines */

/* main */

int main() {
  int n;
  string s;
  cin >> n >> s;

  for (int i = 0; i < n; i++) cs[s[i] - 'a']++;
  //for (int i = 0; i < 26; i++) printf("%d ", cs[i]); putchar('\n');

  int cnt = 0;

  // yuki[a-h]
  for (int i = 0; i < I; i++) {
    int d = min(cs[Y], min(cs[U], min(cs[K], min(cs[I], cs[i]))));
    cnt += d;
    cs[Y] -= d; cs[U] -= d; cs[K] -= d; cs[I] -= d; cs[i] -= d;
    //printf("yuki%c x %d\n", i + 'a', d);
  }
  
  // yukii
  int d = min(cs[Y], min(cs[U], min(cs[K], cs[I] / 2)));
  cnt += d;
  cs[Y] -= d; cs[U] -= d; cs[K] -= d; cs[I] -= d * 2;
  //printf("yukii x %d\n", d);

  // yukj
  for (int i = I + 1; i < K; i++) {
    int d = min(cs[Y], min(cs[U], min(cs[K], cs[i])));
    cnt += d;
    cs[Y] -= d; cs[U] -= d; cs[K] -= d; cs[i] -= d;
    //printf("yukj x %d\n", d);
  }

  // yukk
  d = min(cs[Y], min(cs[U], cs[K] / 2));
  cnt += d;
  cs[Y] -= d; cs[U] -= d; cs[K] -= d * 2;
  //printf("yukk x %d\n", d);

  // yu[l-t]
  for (int i = K + 1; i < U; i++) {
    int d = min(cs[Y], min(cs[U], cs[i]));
    cnt += d;
    cs[Y] -= d; cs[U] -= d; cs[i] -= d;
    //printf("yu%c x %d\n", i + 'a', d);
  }

  // yuu
  d = min(cs[Y], cs[U] / 2);
  cnt += d;
  cs[Y] -= d; cs[U] -= d * 2;
  //printf("yuu x %d\n", d);

  // y[v-x]
  for (int i = U + 1; i < Y; i++) {
    int d = min(cs[Y], cs[i]);
    cnt += d;
    cs[Y] -= d; cs[i] -= d;
    //printf("y%c x %d\n", i + 'a', d);
  }

  // yy
  d = cs[Y] / 2;
  cnt += d;
  cs[Y] -= d * 2;
  //printf("yy x %d\n", d);

  // z
  d = cs[Z];
  cnt += d;
  cs[Z] -= d;
  //printf("z x %d\n", d);

  printf("%d\n", cnt);

  //for (int i = 0; i < 26; i++) printf("%d ", cs[i]); putchar('\n');
  return 0;
}