/in/foo.cc: In function 'int main()':
/in/foo.cc:12:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |                 for(int j=1;j<=a.size();j++)
      |                             ~^~~~~~~~~~
/in/foo.cc:17:36: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   17 |                         if(!(j>='0'&&j<='9'||j>='A'&&j<='Z'))
      |                              ~~~~~~^~~~~~~~