program main
real a
complex b
b=(-4,0)
a=-4
    !! writing cmplx(a) is equivalent to writing a=(-4,0)
    print *, sqrt(cmplx(a))
    !!if you write it directly 
    print*,sqrt(a) 
    !! it wont work bcz here range of sqrt is real 
 print*,sqrt(b)
    !!it is working in these two cases bcz it's range contains all complex number 
end program main