foo.c: In function 'main':
foo.c:10:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d %d %d",&n1,&n2,&n3);
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:13:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&a1[i]);
 ^~~~~~~~~~~~~~~~~~
foo.c:16:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&a2[i]);
 ^~~~~~~~~~~~~~~~~~
foo.c:19:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&a3[i]);
 ^~~~~~~~~~~~~~~~~~