foo.cc: In function 'std::string work(std::string)':
foo.cc:15:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |   for(int j=0;j<s[i].length();j++) {
      |               ~^~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:36:9: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |  while(i<str.length()-1) {
      |        ~^~~~~~~~~~~~~~~
foo.cc:47:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::__cxx11::basic_string<char> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |  for(int i=0;i<res.size()-1;i++) cout<<res[i]<<" ";
      |              ~^~~~~~~~~~~~~

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