function Main(input) {
	input = input.split("\n");
	tmp = input[0].split(" ");
    let takahashiHP = Number(tmp[0])
    let takahashiAtk = Number(tmp[1])
    let aokiHP = Number(tmp[2])
    let aokiAtk = Number(tmp[3])
    aokiHP -= takahashiAtk
  	if(aokiHP <= 0) return console.log('Yes')
  	let i = 1
    while(takahashiHP > 0 || aokiHP > 0) {
      if(i % 2 === 0) aokiHP -= takahashiAtk
      else takahashiAtk -= aokiHP
      
      if(takahashiHP <= 0) {
        return console.log('No')
      } else if(aokiHP <= 0) {
        return console.log('Yes')
      }
    }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));