foo.cc: In function 'int main()':
foo.cc:31:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |    for(int i=o+1;i<=a.size()-1;i++){
      |                  ~^~~~~~~~~~~~
foo.cc:12:6: warning: unused variable 'q' [-Wunused-variable]
   12 |  int q=0;
      |      ^

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