/in/foo.c: In function 'main':
/in/foo.c:7:2: warning: implicit declaration of function 'scanf_s' [-Wimplicit-function-declaration]
  scanf_s("%d%d",&b,&c);
  ^~~~~~~
/in/foo.c:8:12: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if (b%4==0&&b%100!=0||b%400==0)
      ~~~~~~^~~~~~~~~~
/tmp/cc14TNN1.o: In function `main':
foo.c:(.text.startup+0x78): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status