foo.c: In function 'SetUnion':
foo.c:26:6: error: 'i' undeclared (first use in this function)
  for(i=0;i<n1+n2;i++)
      ^
foo.c:26:6: note: each undeclared identifier is reported only once for each function it appears in
foo.c:27:16: error: 'b' undeclared (first use in this function)
   printf("%d ",b[i]);
                ^
foo.c: In function 'Unique':
foo.c:42:6: error: 'i' undeclared (first use in this function)
  for(i=0;i<n;i++)
      ^
foo.c:31:6: warning: variable 'b' set but not used [-Wunused-but-set-variable]
  int b[N]={0};
      ^
foo.c: In function 'main':
foo.c:12:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d",&n1,&n2,&n3);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c: In function 'Read':
foo.c:51:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a[i]);
   ^~~~~~~~~~~~~~~~~

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