foo.cc: In function 'bool row_check(int)':
foo.cc:33:15: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   33 |  if(vec.size()!=len) return false;
      |     ~~~~~~~~~~^~~~~
foo.cc: In function 'bool col_check(int)':
foo.cc:55:15: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   55 |  if(vec.size()!=len) return false;
      |     ~~~~~~~~~~^~~~~

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