foo.cc: In function 'int main()':
foo.cc:11:5: error: 'reverse' was not declared in this scope
   11 |     reverse(s.begin(), s.end());
      |     ^~~~~~~
foo.cc:14:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |     for ( int i = beg; i < s.size(); i ++ ) cout << s[i];
      |                        ~~^~~~~~~~~~

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