/in/foo.c: In function 'main':
/in/foo.c:8:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(a);
  ^~~~
In file included from /in/foo.c:2:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:9:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(b);
  ^~~~
In file included from /in/foo.c:2:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:10:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(c);
  ^~~~
In file included from /in/foo.c:2:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:6:16: warning: variable 'lenc' set but not used [-Wunused-but-set-variable]
  int lena,lenb,lenc;
                ^~~~
/tmp/cc7y3VQ3.o: In function `main':
foo.c:(.text.startup+0x25): warning: the `gets' function is dangerous and should not be used.