  Data sets were collected with the BESIII detector at the BEPCII collider at
the center-of-mass energy of $\sqrt s =$ 3.650 GeV during May 2009 and at
$\sqrt s=$ 3.773 GeV from January 2010 to May 2011. By analyzing the large
angle Bhabha scattering events, the integrated luminosities of the two data
sets are measured %at $\sqrt s=$ 3.650 and 3.773 GeV to be ($\rm
44.49\pm0.02\pm0.44$) $\rm pb^{-1}$ and ($\rm 2916.94\pm0.18\pm29.17$) $\rm
pb^{-1}$, respectively, where the first error is statistical and the second
error is systematic.
