/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", &n, &na, &nb);
  ^~~~~~~
/in/foo.c:83:2: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
  printf("%d %d\n", A, B);
  ^~~~~~
/in/foo.c:83:2: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:83:2: note: include '<stdio.h>' or provide a declaration of 'printf'
/tmp/cccwmO8T.o: In function `main':
foo.c:(.text.startup+0x46): undefined reference to `scanf_s'
foo.c:(.text.startup+0x61): undefined reference to `scanf_s'
foo.c:(.text.startup+0x99): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status