l, r, m, k = map(int,input().split())

if l == r:
    if l%m == 0:
        print("Yes")
    else:
        print('No')
    exit()

if (r-l) >= m:
    print('Yes')
    exit()


ll = l%m
rr = r%m

if (not ll or not rr) or ll > rr:
    print('Yes')
else:
    minim = ll*k
    maxim = rr*k
    if maxim-minim >= m:
        print('Yes')
        exit()
    if minim%m > maxim%m:
        print('Yes')
    elif minim%m == 0 or maxim%m == 0:
        print('Yes')
    else:
        print('No')