foo.cc: In function 'int main(int, const char**)':
foo.cc:6:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("data.in","r",stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:7:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("data.out","w",stdout);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
foo.cc:9:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:11:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&val),mp[val]++;
   ~~~~~~~~~~~~~~~~^~~~~~~~~~

Found 10 testcases.
[Hydro](https://hydro.ac)提供评测服务