rect.cpp: In function 'long long int count_rectangles(std::vector<std::vector<int> >)':
rect.cpp:6:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
6 | for(int i=1;i<a.size()-1;i++){
| ~^~~~~~~~~~~
rect.cpp:7:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
7 | for(int j=1;j<a[i].size()-1;j++){
| ~^~~~~~~~~~~~~~
rect.cpp:8:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
8 | for(int k=i;k<a.size()-1;k++){
| ~^~~~~~~~~~~
rect.cpp:9:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
9 | for(int l=j;l<a[k].size()-1;l++){
| ~^~~~~~~~~~~~~~