import sequtils,strutils
var
    L, R, M, K : int64
    ans : bool
    l,r : int64
(L, R, M, K) =  stdin.readline.split.map(parseBiggestInt)
(l, r) = (L * K, R * K)
if r - l + 1 > M or l mod M == 0:
    echo "Yes"
elif r div M > l div M:
    echo "Yes"
else:
    echo "No"