foo.cc: In member function 'void BigInt::Init(int, int)':
foo.cc:14:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |    for (int j = 0 ; j < a.size () ; j ++ )
      |                     ~~^~~~~~~~~~~
foo.cc: In member function 'BigInt BigInt::operator*(const BigInt&) const':
foo.cc:38:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |         for(int i=0;i<a.size();i++)
      |                     ~^~~~~~~~~
foo.cc:39:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |             for(int j=0;j<b.a.size();j++)
      |                         ~^~~~~~~~~~~
foo.cc:42:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |         for(int i=0;i<c.a.size();i++)
      |                     ~^~~~~~~~~~~

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