let line = readLine()!.split(separator: " ").map({Int($0)!})
var (A, B, C, D) = (line[0], line[1], line[2], line[3])
while A > 0 && C > 0 {
    C -= B
    A -= D
    if C <= 0 {
        print("Yes")
    } else if A <= 0 {
        print("No")
    }
}
