"use strict";
const main = arg => {
  const input = arg.trim().split('\n');
  const arr = input[0].split(" ").map(Number);
  
  let tLife = arr[0];
  const tPower = arr[1];
  let aLife = arr[2];
  const aPower = arr[3];
  
  let cnt = 0;
  
  while(!(tLife <= 0) || !(aLife <= 0)){
        
        if((cnt % 2) === 0){
    		aLife -= tPower;
        }else{
          	tLife -= aPower;
        }
	cnt++;
  }
  
  if(tLife <= 0){
    console.log("No");
  }else{
    console.log("Yes");
  }
}
 
main(require("fs").readFileSync("/dev/stdin", "utf8"));