/in/foo.c: In function 'main':
/in/foo.c:4:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d%d",&n1,&n2);
  ^~~~~
/in/foo.c:4:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:4:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:21:2: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
  printf("%d ",j);
  ^~~~~~
/in/foo.c:21:2: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:21:2: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:5:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k;
          ^
/in/foo.c:18:12: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
   if(a[i]<0&&j<a[i])
      ~~~~~~^~~~~~~~