/in/foo.c: In function 'main':
/in/foo.c:7:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d%d",&n1,&n2);
  ^~~~~
/in/foo.c:7:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:7:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:12:2: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
  printf("%d %d",FindMaxNeg(a,n1),FindMaxNeg(b,n2));
  ^~~~~~
/in/foo.c:12:2: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:12:2: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:12:2: warning: 'max' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%d %d",FindMaxNeg(a,n1),FindMaxNeg(b,n2));
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.c:12:2: warning: 'max' may be used uninitialized in this function [-Wmaybe-uninitialized]
/in/foo.c: In function 'FindMaxNeg':
/in/foo.c:29:9: warning: 'max' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return max;
         ^~~