tickets.cpp: In function 'long long int find_maximum(int, std::vector<std::vector<long long int> >)':
tickets.cpp:12:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
12 | for (int i = 0; i < x.size(); i++) {
| ~~^~~~~~~~~~
tickets.cpp:17:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
17 | for (int i = 0; i < x.size(); i++) {
| ~~^~~~~~~~~~
/usr/bin/ld: /tmp/ccTzoEsC.o: in function `main':
grader.cpp:(.text.startup+0x3b2): undefined reference to `find_maximum(int, std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > >)'
collect2: error: ld returned 1 exit status