foo.cc: In function 'int main()':
foo.cc:7:2: error: 'scarnf' was not declared in this scope
  scarnf("%s",&s1);
  ^~~~~~
foo.cc:7:2: note: suggested alternative: 'scanf'
  scarnf("%s",&s1);
  ^~~~~~
  scanf

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。