import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		char[] arr = sc.next().toCharArray();
		int total = 0;
		int y = 0;
		int vwx = 0;
		int u = 0;
		int lmnopqrst = 0;
		int k = 0;
		int j = 0;
		int i = 0;
		int abcdefgh = 0;
		for (char c : arr) {
		    if (c > 'y') {
		        total++;
		    } else if (c == 'y') {
		        y++;
		    } else if (c > 'u') {
		        vwx++;
		    } else if (c == 'u') {
		        u++;
		    } else if (c > 'k') {
		        lmnopqrst++;
		    } else if (c == 'k') {
		        k++;
		    } else if (c > 'i') {
		        j++;
		    } else if (c == 'i') {
		        i++;
		    } else {
		        abcdefgh++;
		    }
		}
		while (y > 0 && u > 0 && k > 0 && i > 0 && abcdefgh > 0) {
		    y--;
		    u--;
		    k--;
		    i--;
		    abcdefgh--;
		    total++;
		}
		while (y > 0 && u > 0 && k > 0 && i > 1) {
		    y--;
		    u--;
		    k--;
		    i -= 2;
		    total++;
		}
		while (y > 0 && u > 0 && k > 0 && j > 0) {
		    y--;
		    u--;
		    k--;
		    j --;
		    total++;
		}
		while (y > 0 && u > 0 && k > 1) {
		    y--;
		    u--;
		    k -= 2;
		    total++;
		}
		while (y > 0 && u > 0 && lmnopqrst > 0) {
		    y--;
		    u--;
		    lmnopqrst--;
		    total++;
		}
		while (y > 0 && u > 1) {
		    y--;
		    u -= 2;
		    total++;
		}
		while (y > 0 && vwx > 0) {
		    y--;
		    vwx--;
		    total++;
		}
		total += y / 2;
		System.out.println(total);
	}
}