7. From a multi-digit number, several consecutive digits can be extracted to form a new number. For example, from 123456, 1234 can be extracted, as well as 345, 34, etc. If from a multi-digit number, 121, 1122, 2122, 2111, 221, 1212 can be extracted, then the smallest multi-digit number is . $\qquad$
$1212211122$