def r;read_line.split.map &.to_i;end
n,m=r
a=r
g=a.map{[]of Int32}
m.times{
	u,v=r.map &.pred
	g[v]<<u if a[u]>a[v]
	g[u]<<v if a[v]>a[u]
}
r
f=[0]*n
r.each{|i|f[i-1]=1}

ans=(0...n).to_a.sort_by{|i|a[i]}.select{|i|
	if f[i]>0
		f[i]=0
		g[i].map{|j|f[j]^=1}
	end
}
if f.all? 0
	puts ans.size,ans.join '\n',&.succ
else
	p -1
end