foo.cc: In function 'int main()':
foo.cc:7:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&k);
  ~~~~~^~~~~~~~~
foo.cc:11:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&m,&n);
   ~~~~~^~~~~~~~~~~~~~