#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

int main()
{
    int n; string s;
    while (cin>>n>>s) {
        int a[128]={};
        for(char c: s) a[c]++;
        int res=a['z'];
        int Y=a['y'], U=a['u'], K=a['k'], I=a['i'];
        for(int i='v';Y&&i<'y';++i) {
            int m=min(a[i], Y);
            res+=m;
            a[i]-=m;
            Y-=m;
        }
        if (Y and U) {
            for(int i='k'+1;Y&&U&&i<'u';++i) {
                int m=min({a[i], Y, U});
                res+=m;
                a[i]-=m;
                Y-=m; U-=m;
            }
        }
        if (Y and U and K) {
            for(int i='i'+1;Y&&U&&K&&i<'k';++i) {
                int m=min({a[i], Y, U, K});
                res+=m;
                a[i]-=m;
                Y-=m; U-=m; K-=m;
            }
        }
        if (Y and U and K and I) {
            for(int i='a';Y&&U&&K&&I&&i<'z';++i) {
                int m=min({a[i], Y, U, K, I});
                res+=m;
                a[i]-=m;
                Y-=m; U-=m; K-=m; I-=m;
            }
        }
        while (Y and U and K>1) { ++res; --Y, --U, K-=2; }
        while (Y and U>1) { ++res; --Y, U-=2; }
        while (Y>1) { ++res; Y-=2; }
        cout<<res<<endl;
    }
}