   Program PanasonicB
   Implicit none
   Integer(8)::i,j,k

      Read(*,*) i,j
      If (i==1 .OR. j==1) then
         Write(*,*) 1
      Else
         If (MOD(i,2)==0.OR.MOD(j,2)==0) then
            k=i*j/2
         Else
            k=(i-1)*j/2+(j+1)/2
         End If
         Write(*,*) k
      End If
      Stop

   End Program PanasonicB