foo.cc:7:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
    7 | main(){
      |      ^
foo.cc: In function 'int main()':
foo.cc:8:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    8 |  scanf("%lld",&n);
      |  ~~~~~^~~~~~~~~~~

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