Problem: Olesya loves numbers consisting of n digits, and Rodion only likes numbers that are divisible by t. Find some number that satisfies both of them.

Your task is: given the n and t print an integer strictly larger than zero consisting of n digits that is divisible by t. If such number doesn't exist, print  - 1.

Input

The single line contains two numbers, n and t (1 ≤ n ≤ 100, 2 ≤ t ≤ 10) — the length of the number and the number it should be divisible by.

Output

Print one such positive number without leading zeroes, — the answer to the problem, or  - 1, if such number doesn't exist. If there are multiple possible answers, you are allowed to print any of them.

Examples

Input

3 2


Output

712

Solution (in PYTHON):

Solution:
def num(n, t):
    if n == 1 and t == 10: return -1
    if n == 1: return t
    import math
    num = 1
    while int(math.log10(num)) + 1 < n:
        num *= t
    while num != 0 and int(math.log10(num)) + 1 > n:
        num -= t
    if int(math.log10(num)) + 1 == n:
        return num
    return -1

p = raw_input().split(' ')
print num(int(p[0]), int(p[1]))