foo.cc: In function 'int main()':
foo.cc:72:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   72 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
foo.cc:73:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   73 |  for(i = 1; i <= n; i++) scanf("%d", &a[i]);
      |                          ~~~~~^~~~~~~~~~~~~
foo.cc:76:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   76 |  scanf("%d", &Q);
      |  ~~~~~^~~~~~~~~~
foo.cc:78:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   78 |   scanf("%d", &x);
      |   ~~~~~^~~~~~~~~~
foo.cc: In function 'void dfs(int)':
foo.cc:23:35: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   23 |  else if(f[v].x == -2) f[v].s = l & r;
      |                                 ~~^~~
foo.cc:23:35: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]

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Found 20 testcases.
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