public class FakultaetErrechnen {
	
	public FakultaetErrechnen() {
		// TODO Auto-generated constructor stub
	}
	
	public static void main(String[] args) {
		System.out.println("1: "+fak(1));
		System.out.println("2: "+fak(2));
		System.out.println("115: "+fak(115));
		System.out.println("120: "+fak(120));
		System.out.println("125: "+fak(125));
		System.out.println("66: "+fak(66));
		System.out.println("40320: "+fak(40320));
	}
	
	public static int fak(int zahl)
	{

		if (zahl ==1 || zahl==2)
			return zahl;
		
		int zaehler = 2;
		int summe = 1;
		while(summe < zahl )
		{
			summe = 1;
			zaehler++;
			
			for(int x=zaehler; x>1; x--)
			{
				summe *=x;
				
			}
		}
		if (summe == zahl)
			return zaehler;
		return -1;
	}
}