/in/foo.cc: In function 'int get_anc(int, int)':
/in/foo.cc:54:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         return depth[x] - depth[top[x]] - k >= down[top[x]].size() ? 0 : down[top[x]][depth[x] - depth[top[x]] - k];
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc:56:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         return k - depth[x] + depth[top[x]] >= up[top[x]].size() ? 0 : up[top[x]][k - depth[x] + depth[top[x]]];
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~