n,m=gets.split.map &:to_i
l=(1..n).map{gets+?#}+[?#*m]
q=(0...n).map{|i|(0...m).count{|j|l[i][j]!=?#&&[[i+1,j],[i-1,j],[i,j+1],[i,j-1]].count{|a,b|l[a][b]==?.}%2>0}}.inject(:+)
puts q%2>0?:NO:"YES"