import java.util.Arrays;

class Primes {
    public static final int MAX = 50;

    public static void printTrue(boolean flag[]) {
        for (int i = 0; i < flag.length; i++) {
            if (flag[i]) 
                System.out.println(i);
        }
    }

    public static void crossOffMultiples(boolean flag[], int p) {
        for (int mult = 2 * p; mult < flag.length; mult += p)
            flag[mult] = false;
    }

    public static void main(String args[]) {
        // Array to track whether a given number is prime.
        boolean isPrime[] = new boolean[MAX + 1];

        // Initialize all entries (2 and above) to true.
        Arrays.fill(isPrime, true);
        isPrime[0] = false;
        isPrime[1] = false;

        // Cross off multiples of each prime found.
        for (int test = 2; test < isPrime.length; test++) {
            if (isPrime[test])
                crossOffMultiples(isPrime, test);
        }

        // Print everything that hasn't been crossed off.
        printTrue(isPrime);
    }
}