def find_odd(m,n): odd_list = [] for i in range(m,n): if is_odd(i): odd_list.append(i) if len(odd_list) == 0: return 0 sumsum = sum(odd_list) return int(sumsum/len(odd_list))def is_odd(num): while num : yu = num % 10 if yu % 2 == 0: return False num = num // 10 return Trueif __name__ == "__main__": import sys line = input().split(" ") m, n= int(line[0]),int(line[1]) result = find_odd(m, n) print(result)