// Erika Wolfe
// Implements two different sum methods
public class Sum {
    public static void main(String[] args) {
        System.out.println(sum1(5));
        System.out.println(sum2(5));
    }
    
    // pre: n is non-negative
    // post: returns the sum of 1 to n inclusive
    public static int sum1(int n) {
        int sum = 0;
        for (int i = 1; i <= n; i++) {
            sum += i;
        }
        return sum;
    }
    
    // pre: n is non-negative
    // post: returns the sum of 1 to n inclusive
    public static int sum2(int n) {
        return n * (n + 1) / 2;
    }
}