class Reverse {
  public static String rev(String s1) {
    int len = s1.length();
    int i;
    String revs1 = "";
    for(i = len-1; i >= 0; i--) {
      char c = s1.charAt(i);
      revs1 = revs1 + c;
    } // End for(i)
    return revs1;
  } // End rev()

  public static boolean isPrime(int x) {
    int i;
    int counter = 0;
    for(i = 2; i <= x-1; i++) {
      if((x%i) == 0) {
	counter++;
      }
    }
    if(counter > 0) {
      return false;
    } else {
      return true;
    }
  } // End isPrime()

  public static boolean isPrime2(int x) {
    boolean isP = true;
    for(int i = 2; i <= x-1; i++) {
      if((x%i) == 0) {
	isP = false;
	break;
      }
    }
    return isP;
  } // End isPrime2()

  public static boolean isPrime3(int x) {
    boolean isP = true;
    for(int i = 2; i <= x-1; i++) {
      if((x%i) != 0) { continue; }
      isP = false;
      break;
    }
    return isP;
  } // End isPrime3()

  public static boolean isPrime4(int x) {
    int i;
    for(i = 2; i <= x-1; i++) {
      if((x%i) == 0) {
	break;
      }
    }
    // i reaches x only when x is prime
    if(i == x) {
      return true;
    } else {
      return false;
    }
  } // End isPrime4()

  public static boolean isPrime5(int x) {
    for(int i = 2; i <= x-1; i++) {
      if((x%i) == 0) {
	return false;
      }
    }
    return true;
  } // End isPrime5()

  public static void allPrimes(int N) {
    for(int x = 2; x <= N; x++) {
      boolean isP = true;
      for(int i = 2; i <= x-1; i++) {
	if((x%i) != 0) { continue; }
	isP = false;
	break;
      } // End for(i)
      //if(isPrime5(x)) {
      //System.out.println(x + " is prime");
      //}
      if(isP == true) {
	System.out.println(x + " is prime");
      }
    } // End for(x)
  } // End allPrimes()

  public static void main(String[] args) {
    String s = "12345";
    System.out.println("Reverse of " + s + " is " + rev(s));
    s = "abcdef";
    System.out.println("Reverse of " + s + " is " + rev(s));
  } // End main()

} // End class Reverse