/in/foo.c: In function 'main':
/in/foo.c:5:12: warning: zero-length gnu_printf format string [-Wformat-zero-length]
     printf("");
            ^~
/in/foo.c:9:12: warning: too many arguments for format [-Wformat-extra-args]
     printf("\n", n);
            ^~~~
/in/foo.c:20:12: warning: zero-length gnu_printf format string [-Wformat-zero-length]
     printf("");
            ^~