/usr/bin/ld: /tmp/cc7V5yva.o: in function `answer(std::vector<int, std::allocator<int> >)':
grader.cpp:(.text+0xa0): multiple definition of `answer(std::vector<int, std::allocator<int> >)'; /tmp/ccDgEzYU.o:books.cpp:(.text+0xd0): first defined here
/usr/bin/ld: /tmp/cc7V5yva.o: in function `impossible()':
grader.cpp:(.text+0x160): multiple definition of `impossible()'; /tmp/ccDgEzYU.o:books.cpp:(.text+0x170): first defined here
/usr/bin/ld: /tmp/cc7V5yva.o: in function `skim(int)':
grader.cpp:(.text+0x1a0): multiple definition of `skim(int)'; /tmp/ccDgEzYU.o:books.cpp:(.text+0x0): first defined here
/usr/bin/ld: /tmp/cc7V5yva.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccDgEzYU.o:books.cpp:(.text.startup+0x0): first defined here
collect2: error: ld returned 1 exit status