View Compilation Error

0_0_33886358_16173.cpp:24:8: error: conflicting declaration 'int M'
 int N, M, ID;
        ^
0_0_33886358_16173.cpp:16:11: note: previous declaration as 'const int M'
 const int M = 998244353;
           ^
0_0_33886358_16173.cpp: In function 'int main()':
0_0_33886358_16173.cpp:58:16: error: decrement of read-only variable 'M'
         while(M--)
                ^
0_0_33886358_16173.cpp:64:34: error: 'Union' was not declared in this scope
                 Union(id[x],id[y]);
                                  ^