foo.cc: In function 'int main()':
foo.cc:5:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    5 |  scanf("%d %d",&n,&m);
      |  ~~~~~^~~~~~~~~~~~~~~
foo.cc:6:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    6 |  for(int i=1;i<=n;++i)scanf("%d",a+i);
      |                       ~~~~~^~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务