foo.cc: In function 'void work()':
foo.cc:15:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0;i<strlen(input);i++){
               ~^~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:55:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d",&p1,&p2,&p3);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:56:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%s",input);
  ~~~~~^~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务