def to10ss(x, ss):
    r = 0
    d = 0
    while x > 0:
        d = d + x % 10 * ss ** r
    #    print(d, '+', x % 10, '*', ss, '^', r)
        r += 1
        x //= 10
    return d


osn = int(input())
print(to10ss(int(input()), osn))