foo.cc: In function 'int main()':
foo.cc:7:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    7 |                                scanf("%d",&a);
      |                                ~~~~~^~~~~~~~~
foo.cc:6:33: warning: 's' may be used uninitialized in this function [-Wmaybe-uninitialized]
    6 |                                s+=300;
      |                                ~^~~~~

[Hydro](https://hydro.ac)提供评测服务