foo.c: In function 'main':
foo.c:5:2: warning: implicit declaration of function 'scanf_s'; did you mean 'scanf'? [-Wimplicit-function-declaration]
  scanf_s(" %d",&n);
  ^~~~~~~
  scanf
/tmp/ccAGHZDD.o: In function `main':
foo.c:(.text.startup+0x27): undefined reference to `scanf_s'
foo.c:(.text.startup+0x4b): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status

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