foo.c: In function 'unique':
foo.c:26:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
foo.c: In function 'main':
foo.c:31:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n1,&n2);
     ^~~~~~~~~~~~~~~~~~~~~
foo.c:34:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&a1[i]);
         ^~~~~~~~~~~~~~~~~~
foo.c:38:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&a2[i]);
         ^~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务