public class Recursion {

	public static void main(String[] args) {
		for(int i = 10; i <= 20; i++) {
			System.out.printf("%d! == %d\n", i, factorial(i));
		}
	}
	
	public static long factorial(int n) {
		//base case
		if(n == 0) {
			return 1;
		}
		//recursive case
		return n*factorial(n-1);
	}

}