"use strict";

const main = (input) => {
    const spi = input.split('\n');
    let [a, b, c, d] = spi[0].split(' ').map(e => Number(e));

    let turn = true;
    while (a > 0 && c > 0) {
        if (turn) c -= b;
        else a -= d;
        turn = !turn;
    }

    console.log(turn ? "No" : "Yes");
};

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