import sys
input = sys.stdin.readline

L,R,M,K=map(int,input().split())

if R-L>=M-1:
    print("Yes")
    sys.exit()


if (R-L)*K>=M-1:
    print("Yes")
    sys.exit()

L*=K
R*=K

L%=M
R%=M
if R<=L:
    print("Yes")
else:
    print("No")