/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<g[x].size();i++){
                 ~^~~~~~~~~~~~
/in/foo.cc:13:11: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
         if(used[g[x][i].num])
           ^