foo.cc: In function 'int main()':
foo.cc:7:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    7 |  scanf("%f,%f,",&a,&b);
      |  ~~~~~^~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务