#include <iostream>

using namespace std;

int min(int a, int b)
{
	return a < b ? a : b;
}

int gcd(int n, int m)
{
	if (m <= n && n % m == 0)
		return m;
	if (n < m)
		return gcd(m, n);
	else
		return gcd(m, n % m);
}

void countSteps(int a, int b, int n, int &count)
{
	int capacityA = 0;
	int capacityB = 0;

	if (a == n || b == n)
		return ;

	if (capacityA == 0)
	{
		cout << "enter 1\n";
		capacityA = a;
		count++;
	}

	if (capacityB == b)
	{
		cout << "enter 2\n";
		capacityB = 0;
		count++;
	}
	if(capacityA != 0 && capacityB != b)
	{
		cout << "enter 3\n";
		int temp = min(capacityA, b - capacityB);
		count++;
		countSteps(capacityA - temp, capacityB + temp, n, count);
	}
}


int main()
{
	int jug1, jug2, result;
	int count = 0;
	do
		cin >> jug1 >> jug2 >> result;
	while (jug1 < 1 || jug1 > 20 || jug2 < 1 || jug2 > 20);

	if (jug1 < jug2)
		swap(jug1, jug2);

	int x = gcd(jug1, jug2);
	if (result <= jug1 || result <= jug2 && result % x == 0)
	{
		countSteps(jug1, jug2, result, count);
		cout << count << endl;
	}
	else
		cout << "-1" << endl;
	return 0;
}