! 2019.10.27
!
      program answer
      implicit none
      integer :: a,b,x
      double precision :: a_d,b_d,x_d
      double precision :: theta
      double precision :: pi
      intrinsic datan,dble
!
      pi = 3.1415926535897932384626
      read(*,*) a,b,x
      a_d = dble(a)
      b_d = dble(b)
      x_d = dble(x)
      theta = datan(2.0d0*(a_d*b_d)/a_d**2.0d0-2.0d0*(x_d/a_d)
     &/a_d**2.0d0)/pi*180.0d0
      write(*,*) theta
      end program answer