#coding=UTF-8

mojir=input()
hyo=mojir.split(' ')
H=int(hyo[0])
W=int(hyo[1])
N=int(hyo[2])
K=int(hyo[3])

masusu=H*W
makehito=masusu%N
if makehito ==0:
    makehito=N

if K == makehito:
    print('YES')
else:
    print('NO')