foo.c: In function ‘main’:
foo.c:12:18: warning: ‘%lld’ directive writing between 1 and 20 bytes into a region of size 11 [-Wformat-overflow=]
   12 |     sprintf(str,"%lld",num);
      |                  ^~~~
foo.c:12:17: note: directive argument in the range [-9223372036854775808, 999999999]
   12 |     sprintf(str,"%lld",num);
      |                 ^~~~~~
foo.c:12:5: note: ‘sprintf’ output between 2 and 21 bytes into a destination of size 11
   12 |     sprintf(str,"%lld",num);
      |     ^~~~~~~~~~~~~~~~~~~~~~~