public class Euler6 {
    static long solve(long n) {
        long sum = n * (n + 1) / 2;
        long sumSq = n * (n + 1) * (2 * n + 1) / 6;
        return sum * sum - sumSq;
    }

    public static void main(String[] args) {
        assert solve(10) == 2640 : "Checkpoint failed for n=10";
        System.out.println(solve(100));
    }
}