import Foundation

func readInts() -> [Int]{
    readLine()!.split(separator: " ").map { Int($0)! }
}

func main(){
    let line = readInts()
    let(a,b,c,d) = (line[0],line[1],line[2],line[3])
    
    for i in 1...100 {
        if c - b * i <= 0 {
            print("Yes")
            return
        }
        if a - d * i <= 0 {
            print("No")
            return
        }
    }
}
main()
