n,m=gets.split.map &:to_i
g=(0..n).map{[]}
e=(1..m).map{u,v=gets.split.map &:to_i;g[u]<<v;g[v]<<u;[u,v]}
z={}
g[1].map{|v|z[v]=1}
l=g.map{|h|h.select{|v|z[v]}.take(3)}
puts e.any?{|u,v|l[u].any?{|w|l[v].any?{|x|[1,u,v,w,x].uniq.size>4}}}?:YES: :NO