/in/foo.c: In function 'main':
/in/foo.c:8:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s1);
  ^~~~
In file included from /in/foo.c:1:0:
/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(s1);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:7:6: warning: unused variable 'i' [-Wunused-variable]
  int i;
      ^
/in/foo.c: In function 'change':
/in/foo.c:33:4: error: 't' undeclared (first use in this function)
    t[]
    ^
/in/foo.c:33:4: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:33:6: error: expected expression before ']' token
    t[]
      ^
/in/foo.c:21:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,n1,n2;
        ^