/in/foo.c: In function 'main':
/in/foo.c:6:2: warning: implicit declaration of function 'scanf_s' [-Wimplicit-function-declaration]
  scanf_s("%d %d %d", &a, &b, &c);
  ^~~~~~~
/in/foo.c:20:8: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  if (a > c > b)
      ~~^~~
/tmp/ccZFdwq0.o: In function `main':
foo.c:(.text.startup+0x35): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status