#include <bits/stdc++.h>

using namespace std;

const int INF = 1e9;

int cnt[26];

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	string s;
	cin >> n >> s;
	for (int i = 0; i < n; i++) cnt[s[i] - 'a']++;
	int ans = 0;
	int tmp[4];
	string s1 = "yuki";
	for (int i = 0; i < 4; i++) tmp[i] = cnt[s1[i] - 'a'];

	int tmp2 = *min_element(tmp, tmp + 4);
	int tmp3 = 0;
	for (int i = 0; i < 'i' - 'a'; i++) tmp3 += cnt[i];
	tmp3 = min(tmp3, tmp2);
	ans += tmp3;
	for (int i = 0; i < 4; i++) tmp[i] -= tmp3;

	tmp2 = *min_element(tmp, tmp + 3);
	tmp3 = min(tmp[3] / 2, tmp2);
	tmp[3] -= tmp3 * 2;
	for (int i = 0; i < 3; i++) tmp[i] -= tmp3;
	ans += tmp3;

	tmp2 = *min_element(tmp, tmp + 3);
	tmp3 = min(tmp2, cnt['j' - 'a']);
	ans += tmp3;
	for (int i = 0; i < 3; i++) tmp[i] -= tmp3;

	tmp2 = min(tmp[0], tmp[1]);
	tmp3 = min(tmp2, tmp[2] / 2);
	tmp[2] -= tmp3 * 2;
	for (int i = 0; i < 2; i++) tmp[i] -= tmp3;
	ans += tmp3;

	tmp2 = min(tmp[0], tmp[1]);
	tmp3 = 0;
	for (int i = 'l' - 'a'; i < 'u' - 'a'; i++) tmp3 += cnt[i];
	tmp3 = min(tmp3, tmp2);
	ans += tmp3;
	for (int i = 0; i < 2; i++) tmp[i] -= tmp3;

	tmp2 = tmp[0];
	tmp3 = min(tmp2, tmp[1] / 2);
	tmp[1] -= tmp3 * 2;
	tmp[0] -= tmp3;
	ans += tmp3;
	
	tmp3 = 0;
	for (int i = 'v' - 'a'; i < 'y' - 'a'; i++) tmp3 += cnt[i];
	tmp3 = min(tmp3, tmp[0]);
	ans += tmp3;
	tmp[0] -= tmp3;

	ans += tmp[0] / 2;

	ans += cnt['z' - 'a'];

	cout << ans << endl;
	return 0;
}