/in/foo.c: In function 'main':
/in/foo.c:13:10: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
   if(max<abs(a[i+1]-a[i]))
          ^~~
/in/foo.c:20:2: warning: 'p' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%d %d",a[p],a[k]);
  ^~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.c:20:2: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]