public static void main(String[] args) {
		Main r = new Main();
	    var rec = r.factorial(10);
	    System.out.println(rec);
		
	}
	
	
    public int factorial(int n) {
        if (n<0) return -1; 
        if (n == 1 || n == 0) return n;
        return n*factorial(n-1);    
      }
    
    public int sumdigits(int n) {
        if (n<0 || n==0) return 0; 
        return (n%10) + sumdigits(n/10);    
      }

      public double power(int x, int n) {
        if (n<0 || n==0) return -1;
        if (n == 1) return x;
        return x*power(x, n-1);    
      }

      public int gcd(int x, int y) {
        if (y==0) return x;     
        return gcd(y,x%y);    
      }  

      public int tobin(int x) {
        int q = x/2;
        int rm = x%2;
        
        if (q==0) return rm;     
        return rm+10*tobin(q);    
      }