View Compilation Error

0_0_23231780_10662.cpp: In member function 'void chair_tree::update(chair_tree::node*&, int, int)':
0_0_23231780_10662.cpp:83:23: error: 'LS' was not declared in this scope
             t->sum += LS->sum + RS->sum;
                       ^
0_0_23231780_10662.cpp:83:33: error: 'RS' was not declared in this scope
             t->sum += LS->sum + RS->sum;
                                 ^