foo.cc: In function 'void StoI(std::string, BigInt&)':
foo.cc:17:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |         for(int i=0; i<s.size(); i++)
      |                      ~^~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:68:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |         for(int i=0; i<x1.size(); i++)
      |                      ~^~~~~~~~~~
foo.cc:70:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |         for(int i=0; i<x2.size(); i++)
      |                      ~^~~~~~~~~~

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