#!/usr/bin/env python3

import math
import sys

sys.set_int_max_str_digits(10005)

def egcd(a, b):
    if b == 0:
        return (1, 0, a)
    q, r = divmod(a, b)
    x, y, g = egcd(b, r)
    return y, x - q * y, g


def crt(a, m, b, n):
    if n > m:
        a, b = b, a
        m, n = n, m
    x, _, g = egcd(m, n)
    if (a - b) % g != 0:
        return
    x = (b - a) % n * x % n // g * m + a;
    if x <= 0:
        return x + m * n // g
    else:
        return x


def solve():
    b, d, a = map(int, input().split())

    def f(m):
        p10 = pow(10, m)
        n = crt(0, b, (p10 - 1) // 9 * d, p10)
        if not n:
            return False
        else:
            return n <= a

    l = 0
    r = int(a.bit_length() / math.log10(2)) + 5
    while l + 1 < r:
        m = (l + r) // 2
        if f(m):
            l = m
        else:
            r = m
    return l

print(solve())