#include <iostream>
using namespace std;

bool iscontain(int num, int b)
{
	while(num != 0) 
	{
		if(num % 10 == b) return true;
		num /= 10;
	}
	return false;
}
int main()
{
	int S, E, B, K;
	cin >> S >> E >> B >> K;
	bool ans = false;
	for(int i=S; i<=E; i++)
	{
		if(i % B == 0 || iscontain(i, B)) {
			K--;
		}
		if(K == 0) 
		{
			cout << i << endl;
			ans = true;
			break;
		}
	}
	if(!ans) cout << -1 << endl;
}