foo.c: In function 'main':
foo.c:6:3: warning: implicit declaration of function 'sacnf'; did you mean 'sscanf'? [-Wimplicit-function-declaration]
   sacnf("%d%d%d",&a[i]);
   ^~~~~
   sscanf
/tmp/ccu4HVLS.o: In function `main':
foo.c:(.text.startup+0x28): undefined reference to `sacnf'
foo.c:(.text.startup+0x3a): undefined reference to `sacnf'
foo.c:(.text.startup+0x4c): undefined reference to `sacnf'
collect2: error: ld returned 1 exit status

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