highway.cpp: In function 'void dfs(int, int, int)':
highway.cpp:24:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0; i < adj[u].size(); i++){
~~^~~~~~~~~~~~~~~
/tmp/ccqpnVWK.o: In function `f(int, std::vector<int, std::allocator<int> >&, std::vector<int, std::allocator<int> >&)':
highway.cpp:(.text+0x4b9): undefined reference to `ask(std::vector<int, std::allocator<int> >&)'
highway.cpp:(.text+0x4e6): undefined reference to `ask(std::vector<int, std::allocator<int> >&)'
/tmp/ccqpnVWK.o: In function `find_pair(int, std::vector<int, std::allocator<int> >, std::vector<int, std::allocator<int> >, int, int)':
highway.cpp:(.text+0x766): undefined reference to `ask(std::vector<int, std::allocator<int> >&)'
highway.cpp:(.text+0x81d): undefined reference to `ask(std::vector<int, std::allocator<int> >&)'
highway.cpp:(.text+0x986): undefined reference to `ask(std::vector<int, std::allocator<int> >&)'
collect2: error: ld returned 1 exit status