ss = input().split()
a = int(ss[0])
b = int(ss[1])
c = int(ss[2])
ans = 999999999999999999

for i in range(17, -1, -1):
    n = ans
    for j in range(0, 11):
        if j >= 1:
            n -= pow(10, i)
        if n // a * b + (n - n // a) >= c:
            ans = n;

if ans == 999999999999999999 and ans // a * b + (ans - ans // a) < c:
    ans = 1000000000000000000

print(ans)