
function Main (input) {
  var t_life = parseInt(input.split(" ")[0]);
  var t_atk = parseInt(input.split(" ")[1]);
  var a_life = parseInt(input.split(" ")[2]);
  var a_atk = parseInt(input.split(" ")[3]);
  
  for (var counter = 0; a_life >= 0 && t_life >= 0; counter++) {
    if (counter % 2 === 0) {
        // 高橋君の番
        a_life = a_life - t_atk
        if (a_life <= 0) {
        console.log("Yes")
        }
    } else {
        // 青木君の番
        t_life = t_life - a_atk
        if (t_life <= 0) {
        console.log("Yes")
        }
    }
  }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
