foo.c: In function 'main':
foo.c:4:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
  ^~~~~~~~~~~~~~~~~~~
foo.c:5:18: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  for(i=0;i<n;i++)scanf("%d",&a[i]);
                  ^~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务