foo.cc: In function 'void solve()':
foo.cc:8:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    8 |         for (int i = 0; i < s.size(); i++)
      |                         ~~^~~~~~~~~~
foo.cc:11:35: 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 = i; j < s.size(); j++)
      |                                 ~~^~~~~~~~~~
foo.cc:17:28: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   17 |                         if (flag < 0)
      |                            ^

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