n,m=gets.split.map &:to_i
h=Hash.new{|h,k| h[k]=[]}
m.times{
  a,b=gets.split.map &:to_i
  h[b]<<a
}
a=[0]*n

(n-1).downto(0){|i|
  next if a[i]==1
  h[i].each{|e| a[e]=1}
}

puts a.reverse.join.sub(/^0+/, '')