foo.cc:6:1: error: 'stack' does not name a type; did you mean 'obstack'?
 stack<string> stk;
 ^~~~~
 obstack
foo.cc: In function 'void solution(std::__cxx11::string)':
foo.cc:12:3: error: 'stk' was not declared in this scope
   stk.push(tmp);
   ^~~
foo.cc:24:3: error: 'stk' was not declared in this scope
   stk.push(tmp);
   ^~~
foo.cc:34:11: error: 'branck' was not declared in this scope
     top = branck
           ^~~~~~
foo.cc:34:11: note: suggested alternative: 'branch'
     top = branck
           ^~~~~~
           branch
foo.cc:9:9: warning: unused variable 'branch' [-Wunused-variable]
     int branch = top;
         ^~~~~~

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