books.cpp: In function 'void solve(int, int, long long int, int)':
books.cpp:10:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
10 | for(int i=1; i<=v.size()-2; i++)
| ~^~~~~~~~~~~~
books.cpp:12:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
12 | for(int j=i+1; j<=v.size()-1; j++)
| ~^~~~~~~~~~~~
books.cpp:14:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
14 | for(int z=j+1; z<=v.size(); z++)
| ~^~~~~~~~~~