n, m = gets.strip.split(' ').map(&:to_i)
#p n, m
@matrix = []
(1..n).each do |i|
	@matrix[i] = []
end

m.times do
	s, e = gets.strip.split(' ').map(&:to_i)	
	@matrix[s] << e
	@matrix[e] << s
end
#p @matrix

s = 1
path = [s]

def dfs(v, path)
	return if path.length > 5
	@matrix[v].each do |next_v|
		if next_v == 1 && path.length == 5
			puts "YES"
			exit
		end
		if @matrix[v].include?(next_v) && !path.include?(next_v)
			dfs(next_v, path << next_v)
		end
	end
end

dfs(s, path)
puts "NO"