   Program PanasonicB
   Implicit none
   Integer::i,j,k

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

   End Program PanasonicB