/in/foo.c: In function 'main':
/in/foo.c:7:2: warning: implicit declaration of function 'scanf_s' [-Wimplicit-function-declaration]
  scanf_s("%d",&n);
  ^
/in/foo.c:15:2: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long int' [-Wformat=]
  printf("%d",sum);
  ^
/tmp/ccGvFII1.o: In function `main':
foo.c:(.text.startup+0x11): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status