foo.c:2:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
foo.c: In function 'main':
foo.c:9:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&a[i]);
 ^~~~~~~~~~~~~~~~~
foo.c:12:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&b[j]);
 ^~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。