foo.c: In function 'main':
foo.c:16:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   16 |  gets(sa);
      |  ^~~~
In file included from /usr/include/stdio.h:867,
                 from foo.c:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:235:1: note: declared here
  235 | gets (char *__str)
      | ^~~~
foo.c:17:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   17 |  gets(sb);
      |  ^~~~
In file included from /usr/include/stdio.h:867,
                 from foo.c:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:235:1: note: declared here
  235 | gets (char *__str)
      | ^~~~
foo.c:14:8: warning: unused variable 'i' [-Wunused-variable]
   14 |  int n,i;
      |        ^
foo.c:14:6: warning: unused variable 'n' [-Wunused-variable]
   14 |  int n,i;
      |      ^
foo.c: In function 'Concat':
foo.c:11:1: warning: control reaches end of non-void function [-Wreturn-type]
   11 | }
      | ^
foo.c: In function 'main':
foo.c:16:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
   16 |  gets(sa);
      |  ^~~~~~~~
foo.c:17:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
   17 |  gets(sb);
      |  ^~~~~~~~
/usr/bin/ld: /tmp/ccdbUTjo.o: in function `main':
foo.c:(.text.startup+0x4e): warning: the `gets' function is dangerous and should not be used.

[Hydro](https://hydro.ac)提供评测服务