/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:76:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<a1[x].size();i++) c1[a1[x][i]]++;
             ~^~~~~~~~~~~~~
/in/foo.cc:77:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<b1[x].size();i++) c1[b1[x][i]]--;
             ~^~~~~~~~~~~~~
/in/foo.cc:78:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<a2[x].size();i++) c2[a2[x][i]+n]++;
             ~^~~~~~~~~~~~~
/in/foo.cc:79:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i=0;i<b2[x].size();i++) c2[b2[x][i]+n]--;
             ~^~~~~~~~~~~~~