foo.c: In function 'Unique':
foo.c:19:1: warning: control reaches end of non-void function [-Wreturn-type]
   19 | }
      | ^
foo.c: In function 'main':
foo.c:23:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   23 |  scanf("%d%d",&n1,&n2);
      |  ^~~~~~~~~~~~~~~~~~~~~
foo.c:25:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   25 |   scanf("%d",&a1[i]);
      |   ^~~~~~~~~~~~~~~~~~
foo.c:27:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   27 |   scanf("%d",&a2[j]);
      |   ^~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务