foo.cc: In function 'int query(int, int, int)':
foo.cc:47:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0;i < pre.size();++i) {
                    ~~^~~~~~~~~~~~
foo.cc:54:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0;i < pre.size();++i) {
                    ~~^~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:69:17: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
                 if (orz <= n) f[tot].push_back(orz);vis[orz] = 1;
                 ^~
foo.cc:69:53: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
                 if (orz <= n) f[tot].push_back(orz);vis[orz] = 1;
                                                     ^~~