books.cpp: In function 'void solve(int, int, ll, int)':
books.cpp:9:12: error: 'skim' was not declared in this scope
9 | vals[n] = skim(n);
| ^~~~
books.cpp:11:3: error: 'impossible' was not declared in this scope
11 | impossible();
| ^~~~~~~~~~
books.cpp:30:21: error: 'answer' was not declared in this scope
30 | if (sum <= a + a) answer(res);
| ^~~~~~
books.cpp:31:8: error: 'impossible' was not declared in this scope
31 | else impossible();
| ^~~~~~~~~~
books.cpp:44:4: error: 'answer' was not declared in this scope
44 | answer(ans);
| ^~~~~~
books.cpp:56:5: error: 'answer' was not declared in this scope
56 | answer(ans);
| ^~~~~~
books.cpp:59:4: error: 'impossible' was not declared in this scope
59 | impossible();
| ^~~~~~~~~~
books.cpp:63:2: error: 'impossible' was not declared in this scope
63 | impossible();
| ^~~~~~~~~~