import java.util.ArrayList;
import java.util.List;

public class Prime {
    public int current = 0;

    public int nextPrime() {
        while (!Prime.isPrime(++this.current)) {
        }
        return this.current;
    }

    public static double sumOfPrimesBelowN(int n) {
        Prime p = new Prime();
        double total = 0;
        double current = p.nextPrime();
        while (current < n) {
            total += current;
            current = p.nextPrime();
        }
        return total;
    }

    public static Integer[] primesBelow(int i) {
        List<Integer> primes = new ArrayList<Integer>();
        Prime p = new Prime();
        double current = p.nextPrime();
        while (current < i) {
            primes.add((int) current);
            current = p.nextPrime();
        }
        return primes.toArray(new Integer[primes.size()]);
    }

    public static double largestPrimeFactor(double n) {
        Prime p = new Prime();
        double largest = 0;
        double current = p.nextPrime();
        while (current <= n) {
            if (n % current == 0) {
                n /= current;
                if (current > largest) {
                    largest = current;
                }
            }
            current = p.nextPrime();
        }
        return largest;
    }

    public static double nthPrime(int i) {
        int counter = 1;
        Prime p = new Prime();
        double current = p.nextPrime();
        while (counter < i) {
            current = p.nextPrime();
            counter++;
        }
        return current;
    }

    public static double largestPrimeUnder(int i) {
        Prime p = new Prime();
        double largest = 0;
        double current = p.nextPrime();
        while (current < i) {
            if (current > largest) {
                largest = current;
                current = p.nextPrime();
            }
        }
        return largest;
    }

    public static boolean isPrime (int n) {
        if (n <= 1) {
            return false;
        } else if (n == 2) {
            return true;
        } else if (n % 2 == 0) {
            return false;
        }
        for (int i = 3; i <= Math.sqrt(n); i+=2) {
            if (n % i == 0)
                return false;
        }
        return true;
    }
}