View Compilation Error

0_0_2566702_25102.cpp: In function `std::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > > dfs(int)':
0_0_2566702_25102.cpp:72: error: `fu' undeclared (first use this function)
0_0_2566702_25102.cpp:72: error: (Each undeclared identifier is reported only once for each function it appears in.)