/in/foo.c: In function 'main':
/in/foo.c:8:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(str);
  ^~~~
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:28:14: error: 'index' undeclared (first use in this function); did you mean 'index2'?
    s1[j]=str[index[i]+1+j];
              ^~~~~
              index2
/in/foo.c:28:14: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c: In function 'ertoshi':
/in/foo.c:41:2: error: variable-sized object may not be initialized
  int a[n]={0};
  ^~~
/in/foo.c:41:12: warning: excess elements in array initializer
  int a[n]={0};
            ^
/in/foo.c:41:12: note: (near initialization for 'a')