/in/foo.c: In function 'main':
/in/foo.c:61:3: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   gets(a);
   ^~~~
In file included from /in/foo.c:29:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:57:12: warning: unused variable 'k' [-Wunused-variable]
  int n,i,j,k,b;
            ^
/in/foo.c:57:10: warning: unused variable 'j' [-Wunused-variable]
  int n,i,j,k,b;
          ^
/in/foo.c:57:8: warning: unused variable 'i' [-Wunused-variable]
  int n,i,j,k,b;
        ^
/tmp/ccSqDLrb.o: In function `main':
foo.c:(.text.startup+0x3c): warning: the `gets' function is dangerous and should not be used.