View Compilation Error

0_0_25806122_12888.cpp:10:10: error: 'N' was not declared in this scope
  bool mk[N];
          ^
0_0_25806122_12888.cpp: In member function 'void TwoSat::Init()':
0_0_25806122_12888.cpp:13:58: error: 'mk' was not declared in this scope
   For(i,0,n<<1)Can[i].clear(),NO[i].clear(),E[i].clear(),mk[i]=0;
                                                          ^
0_0_25806122_12888.cpp: In member function 'bool TwoSat::dfs(int)':
0_0_25806122_12888.cpp:16:24: error: 'mk' was not declared in this scope
   for(auto y:Can[x])if(mk[y])return 0;
                        ^
0_0_25806122_12888.cpp:17:6: error: 'mk' was not declared in this scope
   if(mk[x])return 1;
      ^
0_0_25806122_12888.cpp:18:3: error: 'mk' was not declared in this scope
   mk[stk[++top]=x]=1;
   ^
0_0_25806122_12888.cpp: In member function 'bool TwoSat::Solve(int)':
0_0_25806122_12888.cpp:30:8: error: 'mk' was not declared in this scope
    if(!mk[i]){
        ^
0_0_25806122_12888.cpp:35:8: error: 'mk' was not declared in this scope
    if(!mk[X[i]]&&!mk[Y[i]])return 0;
        ^