PROGRAM b164
 
IMPLICIT NONE
INTEGER :: A, B, C, D, T1, T2

READ *, A, B, C, D

IF (MOD(C,B) == 0) THEN
	T1 = (C / B) -1
    ELSE 
    T1 = C / B 
END IF

IF (MOD(A,D) == 0) THEN
	T2 = (A / D) -1
    ELSE
    T2 = A / D
END IF
 
IF (T2 < T1) THEN
	PRINT *, 'No'
    ELSE
    PRINT *, 'Yes'
END IF
 
END PROGRAM b164