foo.cc: In function 'int main()':
foo.cc:8:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%f,%f,%c",&a,&b,&c); 
   ~~~~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:24:9: warning: 's' may be used uninitialized in this function [-Wmaybe-uninitialized]
   printf("%.2f",s);
   ~~~~~~^~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务