import streams, sequtils, strutils, algorithm, math, future, sets, tables, hashes
proc `ceilDiv`*[T](x, y: T): T = x div y + ord(x mod y != 0)
proc `//=`*(x: var SomeInteger; y: SomeInteger) = x = x div y
proc `%=`*(x: var SomeInteger; y: SomeInteger) = x = x mod y

var
    T = stdin.readLine.split.map(parseInt)
    L = T[0]
    R = T[1]
    M = T[2]
    K = T[3]
if K == 0 or M == 1:
    echo "Yes"
elif K * R < M:
    if L == 0:
        echo "Yes"
    else:
        echo "No"
elif K * R == M:
    echo "Yes"
elif K * R > M:
    if (R - L) * K >= M:
        echo "Yes"
    else:
        echo "No"
elif L <= M and M <= R:
    echo "Yes"
elif (L div M) < (R div M):
    echo "Yes"
elif K mod 2 == 0:
    if ((R + max(L, R-1)) - (L + min(L+1, R))) <= M:
        echo "Yes"
    else:
        echo "No"
elif K mod 2 == 1:
    echo "No"
else:
    echo "No"
# elif (L div M) == (R div M):
#     var 
#         minmod = L mod M
#         maxmod = R mod M