Lucky Mask

2000ms

262144K

Description:

Petya loves lucky numbers very much. Everybody knows that lucky numbers are positive integers whose decimal record contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

Petya calls a mask of a positive integer n the number that is obtained after successive writing of all lucky digits of number n from the left to the right. For example, the mask of number 72174994 is number 7744, the mask of 7 is 7, the mask of 9999047 is 47. Obviously, mask of any number is always a lucky number.

Petya has two numbers — an arbitrary integer a and a lucky number b. Help him find the minimum number c (c > a) such that the mask of number c equals b.

Input:

The only line contains two integers a and b (1 ≤ a, b ≤ 10⁵). It is guaranteed that number b is lucky.

Output:

In the only line print a single number — the number c that is sought by Petya.

Sample Input:

1 7

Sample Output:

Sample Input:

100 47

Sample Output:

Informação

Provedor Codeforces

Código CF146B