foo.cc: In function 'int main()':
foo.cc:11:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d", &x, &y, &mx, &my);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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