let input = require('fs').readFileSync('/dev/stdin', 'utf8')
.split(/\n| /)
.map(item => parseInt(item))
.slice(0,-1)

let [takahashi_hp, takahashi_atk, aoki_hp, aoki_atk] = input

while(true){
    aoki_hp -= takahashi_atk
    if(aoki_hp <= 0){
        console.log("Yes")
        break
    }
    takahashi_hp -= aoki_atk
    if(takahashi_hp <= 0){
        console.log("No")
        break
    }
}