foo.cc: In function 'long long int cal1()':
foo.cc:17:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |         for(int i=0;i<a.size();i++){
      |                     ~^~~~~~~~~
foo.cc: In function 'long long int cal2()':
foo.cc:33:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |         for(int i=0;i<a.size();i++){
      |                     ~^~~~~~~~~

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