foo.cc: In function 'int main()':
foo.cc:7:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:13:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&x);
   ~~~~~^~~~~~~~~
foo.cc:18:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&x);
    ~~~~~^~~~~~~~~
foo.cc:20:46: warning: iteration 10000 invokes undefined behavior [-Waggressive-loop-optimizations]
   for (int j = 0; j <= MAXN; j ++) f[j] = f[j] & f1[j];
                                           ~~~^
foo.cc:20:21: note: within this loop
   for (int j = 0; j <= MAXN; j ++) f[j] = f[j] & f1[j];
                   ~~^~~~~~~

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