/in/foo.c: In function 'main':
/in/foo.c:13:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(a1);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:14:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(a2);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:18:2: warning: implicit declaration of function 'system' [-Wimplicit-function-declaration]
  system("pause");
  ^~~~~~
/tmp/ccsqj9B8.o: In function `main':
foo.c:(.text.startup+0xb): warning: the `gets' function is dangerous and should not be used.