Wrong Answer
/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:12:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i=0;i<son[x].size();i++){
~^~~~~~~~~~~~~~
/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:12:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i=0;i<son[x].size();i++){
~^~~~~~~~~~~~~~
