foo.cc: In function 'void backtrack(const std::vector<int>&, int, int, std::vector<int>&, std::vector<std::vector<int> >&)':
foo.cc:12:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |     for (int i = start; i < numbers.size(); ++i) {
      |                         ~~^~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:42:23: warning: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
   42 |     for (int i = 0; i < n; i++)
      |                     ~~^~~
foo.cc:47:23: warning: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
   47 |     for (int i = 0; i < c; i++)
      |                     ~~^~~
foo.cc:51:13: warning: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
   51 |         if(m<a) aa.push_back(m);
      |            ~^~
foo.cc:52:14: warning: comparison of integer expressions of different signedness: 'int' and 'unsigned int' [-Wsign-compare]
   52 |         if (m>a)
      |             ~^~

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