View Compilation Error

0_0_25836206_14212.cpp:8:11: error: 'M' was not declared in this scope
 bool mark[M];
           ^
0_0_25836206_14212.cpp: In function 'int main()':
0_0_25836206_14212.cpp:18:15: error: 'size' was not declared in this scope
   rep(q,0,n-1)size[q]=1,fa[q]=q,id[q]=q;
               ^
0_0_25836206_14212.cpp:25:5: error: 'size' was not declared in this scope
     size[x]+=size[y];
     ^
0_0_25836206_14212.cpp:30:7: error: 'size' was not declared in this scope
     --size[find(a)];
       ^
0_0_25836206_14212.cpp:37:20: error: 'size' was not declared in this scope
   rep(q,0,n-1)ans+=size[q]!=0;
                    ^