foo.cc: In function 'int f(std::vector<std::vector<int> >&, std::vector<std::vector<char> >, int, int, int)':
foo.cc:10:6: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |  if(i==vv.size()||j==vv[0].size()) return 0;
      |     ~^~~~~~~~~~~
foo.cc:10:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |  if(i==vv.size()||j==vv[0].size()) return 0;
      |                   ~^~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:26:6: warning: variable 'c1' set but not used [-Wunused-but-set-variable]
   26 |  int c1=0;
      |      ^~

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