import java.util.*; import java.io.*; public class Main { static public class InputIterator{ ArrayList inputLine = new ArrayList(1024); int index = 0; int max; InputIterator(){ BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); while(true){ String read; try{ read = br.readLine(); }catch(IOException e){ read = null; } if(read != null){ inputLine.add(read); }else{ break; } } max = inputLine.size(); } public boolean hasNext(){return (index < max);} public String next(){ if(hasNext()){ String returnStr = inputLine.get(index); index++; return returnStr; }else{ throw new IndexOutOfBoundsException("これ以上入力はないよ。"); } } } static InputIterator ii = new InputIterator(); static void myout(Object t){System.out.println(t);}//standard output static void myerr(Object t){System.err.println(t);}//standard error static String next(){return ii.next();} static int nextInt(){return Integer.parseInt(next());} static long nextLong(){return Long.parseLong(next());} static String[] nextStrArray(){return next().split(" ");} static ArrayList nextIntArray(){ ArrayList ret = new ArrayList(); String[] input = nextStrArray(); for(int i = 0; i < input.length; i++){ ret.add(Integer.parseInt(input[i])); } return ret; } static ArrayList nextLongArray(){ ArrayList ret = new ArrayList(); String[] input = nextStrArray(); for(int i = 0; i < input.length; i++){ ret.add(Long.parseLong(input[i])); } return ret; } static char[] nextCharArray(){return mySplit(next());} static char[] mySplit(String str){return str.toCharArray();} static String kaigyoToStr(String[] list){return String.join("\n",list);} static String kaigyoToStr(ArrayList list){return String.join("\n",list);} static String hanSpToStr(String[] list){return String.join(" ",list);} static String hanSpToStr(ArrayList list){return String.join(" ",list);} public static void main(String[] args){ ArrayList tmp = nextLongArray(); long L = tmp.get(0); long R = tmp.get(1); long M = tmp.get(2); long K = tmp.get(3); long maxL = L * K; long maxR = R * K; if(maxR - maxL >= M){ myout("Yes"); }else{ maxL %= M; maxR %= M; if(maxL >= maxR){ myout("Yes"); }else{ myout("No"); } } } //Method addition frame start //Method addition frame end }