def anagram(s):
    if len(s) % 2 == 1:
        return -1
    s1 = list(s[:len(s) // 2])
    s2 = list(s[len(s) // 2:])
    letters = set(s1 + s2)
    same = 0
    for letter in letters:
        same += min(s1.count(letter), s2.count(letter))
    return (len(s1) + len(s2) - 2 * same) // 2

simple and fullly
def anagram(s):
    t=0
    n=len(s)
    if n%2!=0:
        return -1
    a=s[:n//2]
    b=s[n//2:]
    dicta=dict()
    dictb=dict()
    for i in range(n//2):
        if a[i] not in dicta:
            dicta[a[i]]=1
        else:
            dicta[a[i]]+=1
        if b[i] not in dictb:
            dictb[b[i]]=1
        else:
            dictb[b[i]]+=1
    for i in dicta:
       if i in dictb:
        if dicta[i]>=dictb[i]:
            t+=dictb[i]
        else:
            t+=dicta[i]
    t=n//2-t
    return t

int anagram(string s) {
    if(s.size() % 2 == 1) return -1;
    map<char, int> mp;
    int ans = 0;
    for(int i = 0; i < s.size() / 2; i++) mp[s[i]]++;
    for(int i = s.size() / 2; i < s.size(); i++){
        if(mp[s[i]] != 0) mp[s[i]]--;
        else ans++;
    }
    return ans;
}

sub anagram {
    my $s = shift;
    my %h1;
    my $cnt = 0;

    if (length($s) % 2) {
        return -1;
    }

    my $s1 = substr($s, 0, length($s) / 2);
    my @s2 = split("", substr($s, length($s) / 2, length($s)));

    
    foreach (split("", $s1)) {
        $h1{$_} += 1;
    }

    foreach my $k (@s2) {
        if (defined($h1{$k}) && $h1{$k} != 0) {
            $h1{$k} -= 1;            
        }
        else {
            $cnt++;
        }        
    }

    return $cnt;
}