const Main = () => {
    const line = require('fs').readFileSync('/dev/stdin', 'utf8');
    let [tHp, tAtk, aHp, aAtk] = line.split(' ').map(v => parseInt(v, 10));
    while (true) {
        aHp -= tAtk;
        if (aHp <= 0) {
            console.log('Yes');
            break;
        }
        tHp -= aAtk;
        if (tHp <= 0) {
            console.log('No');
            break;
        }
    }
}

Main();