/in/foo.cc: In function 'int main()':
/in/foo.cc:11:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |         for(int j=0;j<s.size();j++)if(s[j]>='A'&&s[j]<='Z')s[j]=s[j]-'A'+'a';
      |                     ~^~~~~~~~~