program ABC_077_B_AroundSquare
   implicit none
   integer(8) N, i
   read(*, *) N
   do i = 1, N
      if( i ** 2 <= N .and. (i+1) ** 2 > N) then
	      write(*, *) i ** 2
		  exit
	  end if
   end do
end program ABC_077_B_AroundSquare