/in/foo.cc: In function 'int main()':
/in/foo.cc:70:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |     for(int i=0; i<a.size();i++){
      |                  ~^~~~~~~~~
/in/foo.cc: In function 'int bfs()':
/in/foo.cc:64:1: warning: control reaches end of non-void function [-Wreturn-type]
   64 | }
      | ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:76:11: warning: 'z' may be used uninitialized [-Wmaybe-uninitialized]
   76 |     a += z+'0';
      |          ~^~~~
/in/foo.cc:69:9: note: 'z' was declared here
   69 |     int z;
      |         ^