/in/foo.c: In function 'main':
/in/foo.c:13:2: warning: implicit declaration of function 'scanf_s' [-Wimplicit-function-declaration]
  scanf_s("%d", &n);
  ^~~~~~~
/in/foo.c:15:23: warning: unused variable 'cnt' [-Wunused-variable]
  long long a[100000], cnt = 0;
                       ^~~
/tmp/ccGdHznC.o: In function `main':
foo.c:(.text.startup+0x1e): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status