foo.c: In function 'main':
foo.c:13:6: error: 'i' undeclared (first use in this function)
  for(i=0;i<n2;i++)
      ^
foo.c:13:6: note: each undeclared identifier is reported only once for each function it appears in
foo.c:10:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n1,&n2);
  ^~~~~~~~~~~~~~~~~~~~~
foo.c:12:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a[i]);
   ^~~~~~~~~~~~~~~~~

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