library.cpp: In function 'void Solve(int)':
library.cpp:24:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
24 | for(int i = 0; i < books.size(); ++ i) {
| ~~^~~~~~~~~~~~~~
library.cpp:26:23: error: 'Query' was not declared in this scope
26 | int ans = Query(M);
| ^~~~~
library.cpp:40:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
40 | for(int i = 0; i < books.size(); ++ i) {
| ~~^~~~~~~~~~~~~~
library.cpp:42:23: error: 'Query' was not declared in this scope
42 | int ans = Query(M);
| ^~~~~
library.cpp:57:5: error: 'Answer' was not declared in this scope
57 | Answer(res);
| ^~~~~~