use warnings;
use strict;

for(51..66){
    my $s = sprintf("%b", 2**$_-1);
    print "$_:" . length($s) . "\n";
}

##</code><code>##

51:51
52:52
53:53
54:54
55:55
56:56
57:57
58:58
59:59
60:60
61:61
62:63 *
63:64 *
64:64 *
65:64 *
66:64 *