foo.c: In function 'main':
foo.c:10:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&m);
   ^~~~~~~~~~~~~~
foo.c: In function 'distance':
foo.c:21:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lf %lf %lf %lf",&a[i][0],&a[i][1],&a[i][2],&a[i][3]);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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