answer.code: In function ‘int main()’:
answer.code:11:12: error: invalid conversion from ‘int’ to ‘const char*’ [-fpermissive]
   11 | len=strlen(len);
      |            ^~~
      |            |
      |            int
In file included from answer.code:2:
/usr/include/string.h:385:35: note:   initializing argument 1 of ‘size_t strlen(const char*)’
  385 | extern size_t strlen (const char *__s)
      |                       ~~~~~~~~~~~~^~~