const Main = input => {
  const inp = input.split(" ");
  let a = parseInt(inp[0], 10);
  const b = parseInt(inp[1], 10);
  let c = parseInt(inp[2], 10);
  const d = parseInt(inp[3], 10);
  
  let takahashiWin = false;
  let i = 0;
  while(true) {//attack
    if(i % 2 === 0) {
      c -= b;
    } else {
      a -= d;
    }
    
    if(a <= 0) {//takahashi lose
      console.log("No");
      break;
    }
    if(c <= 0) {//takahashi win
      console.log("Yes");
      break;
    }
    
    i++;
  }
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));