/in/foo.cc:4:13: error: 'MAX' was not declared in this scope
 int n,m,s,a[MAX][MAXN];
             ^~~
/in/foo.cc: In function 'void go(int, int)':
/in/foo.cc:22:13: error: 'a' was not declared in this scope
  for(i=1;i<=a[x][0];i++){
             ^
/in/foo.cc:7:19: warning: unused variable 'k' [-Wunused-variable]
  register int i,j,k;
                   ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:35:23: error: 'sync_with_stdio' was not declared in this scope
  ios:sync_with_stdio(0);
                       ^
/in/foo.cc:39:6: error: redeclaration of 'int i'
  int i,x,y;
      ^
/in/foo.cc:37:15: note: 'int i' previously declared here
  register int i,j,k; 
               ^
/in/foo.cc:43:3: error: 'a' was not declared in this scope
   a[x][++a[x][0]]=y;
   ^
/in/foo.cc:45:3: error: 'a' was not declared in this scope
   a[y][++a[y][0]]=x;
   ^
/in/foo.cc:37:17: warning: unused variable 'j' [-Wunused-variable]
  register int i,j,k; 
                 ^
/in/foo.cc:37:19: warning: unused variable 'k' [-Wunused-variable]
  register int i,j,k; 
                   ^
/in/foo.cc:35:2: warning: label 'ios' defined but not used [-Wunused-label]
  ios:sync_with_stdio(0);
  ^~~