#include<iostream>
using namespace std;
int main()
{
	int x, y, n;
	cin >> x >> y >> n;
	if (n < 10)
	{
		cout << n * (x - 1);
	}
	if (n >= 10)
	{
		int a, b;
		a = n * (x - 1);
		b = (n / 10) * (y - 1) + (n % 10) * (x - 1);
		if (a <= b) cout << a;
		if (a > b) cout << b;
	}
	return 0;
}