N, M = gets.split.map &:to_i
S = $<.map { |s| eval "[%d, %d].sort" % s.split }
deg = [0] * N
S.each { |t| deg[t[0]] += 1; deg[t[1]] += 1 }
odd = (0...N).select { |i| deg[i] % 2 == 1 }
puts odd.size > 2 ? :NO : :YES