/in/foo.cc: In function 'int main()':
/in/foo.cc:11:10: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(a1);
          ^
In file included from /usr/include/c++/7/cstdio:42:0,
                 from /usr/include/c++/7/ext/string_conversions.h:43,
                 from /usr/include/c++/7/bits/basic_string.h:6159,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:12:10: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(b1); 
          ^
In file included from /usr/include/c++/7/cstdio:42:0,
                 from /usr/include/c++/7/ext/string_conversions.h:43,
                 from /usr/include/c++/7/bits/basic_string.h:6159,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/tmp/ccoiS7hT.o: In function `main':
foo.cc:(.text.startup+0x6c): warning: the `gets' function is dangerous and should not be used.