View Compilation Error

0_0_13052993_6369.cpp:57: error: invalid token
0_0_13052993_6369.cpp:57: error: invalid token
0_0_13052993_6369.cpp: In member function `int Palindromic_Tree::add(int)':
0_0_13052993_6369.cpp:57: error: non-lvalue in unary `&'
0_0_13052993_6369.cpp:57: error: `a' undeclared (first use this function)
0_0_13052993_6369.cpp:57: error: (Each undeclared identifier is reported only once for each function it appears in.)