#include <stdio.h>
#include <algorithm>

int main() {
    int a[9] = {0};
    int n;
    char c;
    scanf("%d\n",&n);
    for(int i=0;i<n;i++){
        scanf("%c",&c);
        if      (c <= 'h') a[0]++;
        else if (c == 'i') a[1]++;
        else if (c == 'j') a[2]++;
        else if (c == 'k') a[3]++;
        else if (c <= 't') a[4]++;
        else if (c == 'u') a[5]++;
        else if (c <= 'x') a[6]++;
        else if (c == 'y') a[7]++;
        else               a[8]++;
    }
    int happy=a[8];
    a[8]=0;
    if (a[7] && a[6]) {
        int dd=std::min({a[7],a[6]});
        happy+=dd;
        a[7]-=dd;
        a[6]-=dd;
    }
    if (a[7] && a[5] && a[4]) {
        int dd=std::min({a[7],a[5],a[4]});
        happy+=dd;
        a[7]-=dd;
        a[5]-=dd;
        a[4]-=dd;
    }
    if (a[7] && a[5] && a[3] && a[2]) {
        int dd=std::min({a[7],a[5],a[3],a[2]});
        happy+=dd;
        a[7]-=dd;
        a[5]-=dd;
        a[3]-=dd;
        a[2]-=dd;
    }
    if (a[7] && a[5] && a[3] && a[1] && a[0]) {
        int dd=std::min({a[7],a[5],a[3],a[1],a[0]});
        happy+=dd;
        a[7]-=dd;
        a[5]-=dd;
        a[3]-=dd;
        a[1]-=dd;
        a[0]-=dd;
    }
    if (a[7] && a[5] && a[3] && (a[1]>=2)) {
        int dd=std::min({a[7],a[5],a[3],a[1]/2});
        happy+=dd;
        a[7]-=dd;
        a[5]-=dd;
        a[3]-=dd;
        a[1]-=(2*dd);
    }
    if (a[7] && a[5] && (a[3]>=2)) {
        int dd=std::min({a[7],a[5],a[3]/2});
        happy+=dd;
        a[7]-=dd;
        a[5]-=dd;
        a[3]-=(2*dd);
    }
    if (a[7] && (a[5]>=2)) {
        int dd=std::min({a[7],a[5]/2});
        happy+=dd;
        a[7]-=dd;
        a[5]-=(2*dd);
    }

    printf ("%d\n",happy);
}