foo.cc: In function 'int main()':
foo.cc:10:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |  for (int i = 0; i < a.size(); i++)
      |                  ~~^~~~~~~~~~
foo.cc:14:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |  for (int i = 0; i < b.size(); i++)
      |                  ~~^~~~~~~~~~
foo.cc:28:7: warning: unused variable 'x' [-Wunused-variable]
   28 |   int x = -1;
      |       ^

[Hydro](https://hydro.ac)提供评测服务