View Compilation Error

0_0_6546873_4417.cpp: In function `void dfs(int&, std::string&)':
0_0_6546873_4417.cpp:27: error: invalid initialization of non-const reference of type 'int&' from a temporary of type 'int'
0_0_6546873_4417.cpp:14: error: in passing argument 1 of `void dfs(int&, std::string&)'