foo.cc: In function 'int main()':
foo.cc:10:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |         for(int i=0;i<s.length();i++)
      |                     ~^~~~~~~~~~~
foo.cc:9:13: warning: variable 'topt' set but not used [-Wunused-but-set-variable]
    9 |         int topt=0,flag=true;
      |             ^~~~

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