foo.cc: In function 'std::string fun(std::string, std::string)':
foo.cc:16:17: warning: comparison of integer expressions of different signedness: 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   16 |   if (v1.size() < len1 - i)v1.push_back(mult);
      |       ~~~~~~~~~~^~~~~~~~~~
foo.cc:20:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |  for (int i = 0; i < v1.size(); i++)while (v1[i].size() < v1[v1.size() - 1].size())v1[i].push_back(0);
      |                  ~~^~~~~~~~~~~
foo.cc:26:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |   for (int j = 0; j < v1.size(); j++)sum += v1[j][i];
      |                   ~~^~~~~~~~~~~
foo.cc:21:6: warning: unused variable 'temp' [-Wunused-variable]
   21 |  int temp = v1[0].size();
      |      ^~~~

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