foo.c: In function 'main':
foo.c:7:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d",&n1,&n2,&n3);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:11:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a1[i]);
    ^~~~~~~~~~~~~~~~~~
foo.c:15:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a2[i]);
    ^~~~~~~~~~~~~~~~~~
foo.c:17:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a3[i]);
    ^~~~~~~~~~~~~~~~~~

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