/in/foo.c: In function 'main':
/in/foo.c:11:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s1);
  ^~~~
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:12:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s2);
  ^~~~
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:13:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s3);
  ^~~~
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:10:7: warning: unused variable 'c' [-Wunused-variable]
  char c;char *p;
       ^
/in/foo.c:9:8: warning: unused variable 'len' [-Wunused-variable]
  int i,len;
        ^~~
/in/foo.c:9:6: warning: unused variable 'i' [-Wunused-variable]
  int i,len;
      ^
/in/foo.c: In function 'jiaohuan':
/in/foo.c:26:6: warning: unused variable 'i' [-Wunused-variable]
  int i;
      ^
/tmp/ccXsOA7K.o: In function `main':
foo.c:(.text.startup+0x1e): warning: the `gets' function is dangerous and should not be used.