from sys import stdin
def main():
    #入力
    readline=stdin.readline
    L,R,M,K=map(int,readline().split())
    mi=L*K
    ma=R*K
    if ma-mi>=M:
        print("Yes")
    else:
        if mi%M==0:
            print("Yes")
        else:
            if mi%M>ma%M:
                print("Yes")
            else:
                print("No")
if __name__=="__main__":
    main()