"""
Given two number a and b (1 <= a <= b <= 10^6). Find most frequent digit among all prime numbers between a and b inclusive.
if frequency is same print highest digit.

Example: from 1 to 20, prime numbers are - 2, 3, 5, 7, 11, 13, 17, 19.
Here 2, 5, 9 occur only once, 3, 7 occur twice, and 1 occurs 5 times. So the result is 1.
"""