rect.cpp: In function 'long long int count_rectangles(std::vector<std::vector<int> >)':
rect.cpp:20:21: 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 r1 = 1; r1 < a.size()-1; ++r1){
| ~~~^~~~~~~~~~~~
rect.cpp:21:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
21 | for(int r2 = r1; r2 < a.size()-1; ++r2){
| ~~~^~~~~~~~~~~~
rect.cpp:22:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
22 | for(int c1 = 1; c1 < a[0].size()-1; ++c1){
| ~~~^~~~~~~~~~~~~~~
rect.cpp:23:37: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
23 | for(int c2 = c1; c2 < a[0].size()-1; ++c2){
| ~~~^~~~~~~~~~~~~~~