# coding : utf-8

L, R, M, K = gets.split(' ').map{|s|s.to_i}

lmm = (L * K) % M
rmm = (R * K) % M
lpm = (L * K) / M
rpm = (R * K) / M

if L * K == 0 && R * K == 0 then
  puts "Yes"
elsif lmm == 0 || lpm < rpm then
  puts "Yes"
else
  puts "No"
end