foo.c: In function 'main':
foo.c:13:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&k1,&k2);
  ^~~~~~~~~~~~~~~~~~~~~
foo.c: In function 'fb':
foo.c:9:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^
foo.c: In function 'main':
foo.c:15:6: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
   sum+=fb(i);
      ^~

[Hydro](https://hydro.ac)提供评测服务