Given a number. Tell the largest prime that can be formed by removing some digits from front and back of that number
eg-21342 || largest prime=13 (by removing 2 from front and 42 from back)
eg-197 ||largest prime=197(remove nothing from front and back)
Note-if there exist no prime number print "0"
eg- 44 || ans=0 as there exist no prime number
INPUT FORMAT- Input is of only one line containing a number
OUTPUT FORMAT- output is the largest prime formed by removing Digits from back and front
Sample Input-
22173264
Sample Output-
173