function Main (input) {
  input = input.split("\n")[0].split(" ").map(Number);
  var h1 = input[0];
  var s1 = input[1];
  var h2 = input[2];
  var s2 = input[3];
  var tr = 0;
  while (true) {
    if (h1 <= 0) {
      console.log("No");
      break;
    }
    else if (h2 <= 0) {
      console.log("Yes");
      break;
    }
    else {
      if (tr) {
        h1 -= s2;
      }
      else {
        h2 -= s1;
      }
      tr == 0 ? tr = 1 : tr = 0
    }
  }
}

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