city.cpp: In function 'void build_tree()':
city.cpp:35:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, std::pair<int, int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
35 | for(int i=0;i<cur.size();i++){
| ~^~~~~~~~~~~
city.cpp:36:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, std::pair<int, int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
36 | while(j<cur.size() && cur[j].first <= cur[i].first) j++;
| ~^~~~~~~~~~~
city.cpp:37:8: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, std::pair<int, int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
37 | if(j == cur.size()) break;
| ~~^~~~~~~~~~~~~
/tmp/cco3DMty.o: In function `main':
city.cpp:(.text.startup+0x0): multiple definition of `main'
/tmp/ccdZcKgs.o:grader.cpp:(.text.startup+0x0): first defined here
collect2: error: ld returned 1 exit status