awk -v S="X" '
        BEGIN {
                n = split( "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z", A )
                for ( i = 1; i <= n; i++ )
                {
                        if ( A[i] == S )
                                s_idx = i
                }
        }
        {
                R[$1]
                next
        }
        END {
                if ( s_idx > 1 )
                {
                        for ( j = s_idx; j <= n; j++ )
                        {
                                if ( A[j] in R )
                                        print A[j]
                        }
                        for ( k = 1; k < s_idx; k++ )
                        {
                                if ( A[k] in R )
                                        print A[k]
                        }
                }
                else
                {
                        for ( j = 1; j <= n; j++ )
                        {
                                if ( A[j] in R )
                                        print A[j]
                        }
                }
        }
' filename