\[\boxed{\mathbf{156.}}\]
\[300 + 50 = 350\]
\[300 + 2 = 302\]
\[300 + 52 = 352\]
\[350 + 2 = 352\]
\[520 + 4 = 524\]
\[500 + 24 = 524\]
\[504 + 20 = 524\]
\[500 + 4 = 504\]
\[600 + 7 = 607\]
\[630 + 7 = 637\]
\[600 + 30 = 630\]
\[607 + 30 = 637\]
\[800 + 40 = 840\]
\[809 + 40 = 849\]
\[800 + 49 = 849\]
\[800 + 9 = 809\]