"use strict"
function main(arg) {
    var p = arg.trim().split("\n")[0].split(" ").map(Number)
    let A = p[0]
    let B = p[1]
    let C = p[2]
    let D = p[3]
    let ans = 'Yes'
    for (let i = 0; i < 200; i++) {
        if (i % 2 === 0) {
            // t
            C -= B
            if (C <= 0) {
                ans = 'Yes'
                break
            }
        } else {
            // a
            A -= D
            if (A <= 0) {
                ans = 'No'
                break
            }
        }
    }
    console.log(ans)
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));