#include <iostream>
using namespace std;

int main()
{
	int x,y,n;
	cin >> x >> y >> n;
	x--;
	y--;
	int a = n * x;
	int b = n % 10 * x + n / 10 * y;
	if(a >= b) cout << b;
	else cout << a;
	return 0;
}

80分求救，最后两个点WA