foo.cc: In function 'int main()':
foo.cc:10:18: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |         for(i=0;i<s.size();i++)
      |                 ~^~~~~~~~~
foo.cc:13:18: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |         for(i=0;i<s.size();i++)
      |                 ~^~~~~~~~~
foo.cc:21:20: error: expected ';' before ':' token
   21 |                 k++:
      |                    ^
      |                    ;

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