foo.c: In function 'unique':
foo.c:23:2: warning: statement with no effect [-Wunused-value]
  for(i;i<n;i++)
  ^~~
foo.c: In function 'main':
foo.c:6:10: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  int n1; scanf("%d",&n1);
          ^~~~~~~~~~~~~~~
foo.c:7:10: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  int n2; scanf("%d",&n2);
          ^~~~~~~~~~~~~~~
foo.c:10:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a1[i]); 
   ^~~~~~~~~~~~~~~~~~
foo.c:14:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a2[i]); 
   ^~~~~~~~~~~~~~~~~~

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