class FactSum {
    static int factorial(int n){
	if (n <=0) return 1;
	else return n*factorial(n-1);    
};

    static int doSum(int n){
	int s=0;
	while (n >= 0) {
	    s = s + factorial(n);
	    n=n-1;
	}
	return s;
    }
};