foo.cc: In function 'int main()':
foo.cc:51:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n); scanf("%s",key);
 ~~~~~^~~~~~~~~
foo.cc:51:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n); scanf("%s",key);
                 ~~~~~^~~~~~~~~~
foo.cc:57:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%%",p+j);
 ~~~~~^~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务