foo.c: In function 'main':
foo.c:43:25: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
   43 |                 s = s + abs(a[i] - X) + abs(b[i] - Y);
      |                         ^~~
foo.c:4:1: note: include '<stdlib.h>' or provide a declaration of 'abs'
    3 | #include<math.h>
  +++ |+#include <stdlib.h>
    4 | int main()

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