/in/foo.cc: In function 'BigInt add(BigInt, BigInt)':
/in/foo.cc:11:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |     for (int i = 0; i < a.size() || i < b.size(); i++) {
      |                     ~~^~~~~~~~~~
/in/foo.cc:11:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |     for (int i = 0; i < a.size() || i < b.size(); i++) {
      |                                     ~~^~~~~~~~~~
/in/foo.cc:12:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |         int x = i < a.size() ? a[i] : 0;
      |                 ~~^~~~~~~~~~
/in/foo.cc:13:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |         int y = i < b.size() ? b[i] : 0;
      |                 ~~^~~~~~~~~~
/in/foo.cc: In function 'BigInt multiply(BigInt, BigInt)':
/in/foo.cc:24:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |     for (int i = 0; i < a.size(); i++) {
      |                     ~~^~~~~~~~~~
/in/foo.cc:26:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |         for (int j = 0; j < b.size(); j++) {
      |                         ~~^~~~~~~~~~