foo.cc: In function 'int Solve(std::string)':
foo.cc:7:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 |         for(int i=0;i<s.length();i++)
      |                     ~^~~~~~~~~~~
foo.cc:6:19: warning: unused variable 'k' [-Wunused-variable]
    6 |         int sum=0,k=0;
      |                   ^
foo.cc: In function 'int main()':
foo.cc:27:13: warning: unused variable 'k' [-Wunused-variable]
   27 |         int k=Solve(s);
      |             ^

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