links.cpp: In function 'void dfs(int)': links.cpp:29: warning: comparison between signed and unsigned integer expressions links.cpp: In function 'int main()': links.cpp:46: warning: comparison between signed and unsigned integer expressions links.cpp:57: warning: comparison between signed and unsigned integer expressions links.cpp:66: warning: comparison between signed and unsigned integer expressions links.cpp:85: warning: comparison between signed and unsigned integer expressions links.cpp:92: warning: comparison between signed and unsigned integer expressions links.cpp:99: warning: comparison between signed and unsigned integer expressions