\[\boxed{\mathbf{394.}}\]
\[340 + 183 = 523\]
\[523 - 183 = 340\]
\[340 - 183 = 157\]
\[157 + 183 = 340\]
\[537 + 209 = 746\]
\[746 - 209 = 537\]
\[537 - 209 = 328\]
\[328 + 209 = 537\]
\[462 + 358 = 820\]
\[820 - 358 = 462\]
\[462 - 358 = 104\]
\[358 + 104 = 462\]
\[704 + 296 = 1000\]
\[1000 - 704 = 296\]
\[704 - 296 = 408\]
\[408 + 296 = 704\]