View Compilation Error

0_0_35976520_12812.cpp:12:7: error: 'MAXM' was not declared in this scope
 }edge[MAXM << 1];
       ^
0_0_35976520_12812.cpp: In function 'void add_edge(int, int, int)':
0_0_35976520_12812.cpp:21:5: error: 'edge' was not declared in this scope
     edge[node].to = v;
     ^
0_0_35976520_12812.cpp: In function 'void dfs(int, int)':
0_0_35976520_12812.cpp:32:32: error: 'edge' was not declared in this scope
  for (int i = head[u]; ~i; i = edge[i].pre) {
                                ^