public class Solution {
    public int factorial(int value) {
        /* improve
        if (value < 0) {
            throw new IllegalArgumentException(
                "Factorial is not defined for negative integers"
            );
        }
        */

        if (value == 0 || value == 1) return 1;


        int result = 1;

        for (int i = 2; i <= value; i++) {
            result *= i;
        }

        return result;
    }
}