foo.cc: In function 'int main()':
foo.cc:13:22: 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=0;i<s.size();i++)
      |                     ~^~~~~~~~~
foo.cc:23:17: warning: unused variable 'i' [-Wunused-variable]
   23 |         for(int i=j;j>=1;j--)
      |                 ^

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