#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU
############################################################
def gs() gets.chomp end
def gi() gets.to_i end
def gf() gets.to_f end
def gss() gs.split end
def gis() gss.map(&:to_i) end
def gfs() gss.map(&:to_f) end
def nmapf(n,f) n.times.map{ __send__ f } end
def ngs(n) nmapf n,:gs end
def ngi(n) nmapf n,:gi end
def ngss(n) nmapf n,:gss end
def ngis(n) nmapf n,:gis end
def arr2d(h,w,v=0) h.times.map{[v] * w} end
def for2p(hr,wr,&pr) hr.each{|i|wr.each{|j| yield(i,j)}} end
def nsum(n) n * (n + 1) / 2 end
def vcount(d,r=Hash.new(0)) d.inject(r){|r,e| r[e]+=1;r} end
############################################################

n, x = gis
a = gis.each_with_index.to_a.sort_by{|i,j|-i}

m = {0 => []}

def tos(a,r)
    s = ""
    a.each_with_index do |v,i|
        if r.include? i
            s << "o"
        else
            s << "x"
        end
    end
    s
end

a.each do |v,i|
    m.keys.sort.reverse_each do |k|
        m[k + v] = m[k] + [i]
        if k + v == x
            puts tos(a, m[k] + [i])
            exit
        end
    end
end

if !m.key?(x)
    puts "No"
    exit
end

puts tos(a, m[x])