foo.c: In function 'v':
foo.c:6:4: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
  k=abs(x[i]-x[j])+abs(y[i]-y[j]);
    ^~~
foo.c: In function 'main':
foo.c:11:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ^~~~~~~~~~~~~~
foo.c:14:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&n2);
    ^~~~~~~~~~~~~~~

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