foo.cc: In function 'int main()':
foo.cc:13:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |     for(int i=1;i<=a.size();i++)
      |                 ~^~~~~~~~~~
foo.cc:15:18: 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 i=1;i<=b.size();i++)
      |                 ~^~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务