local ffi = require 'ffi'
local C, ct = ffi.C, ffi.typeof 'uint64_t[1]'
ffi.cdef 'int scanf(const char *, ...);'

print((function (f)
	return f(ct(),ct(),ct(),ct()) and "YES" or "NO"
end)(function (h, w, n, k)
	C.scanf("%lu%lu%lu%lu",h,w,n,k)
	local t=h[0]*w[0]
	if t<=n[0] then return t==k[0] end
	if t%n[0]==k[0] then return true end
	if n[0]==k[0] and t%n[0]==0 then return true end
	return false
end))