import java.util.*;

public class LongestSequence { private static final double EPSILON = 0.00001;

// Evaluate all arithmetic operations of any two elements of "numbers", mark their result in "used" as true
private static void eval(List<Double> numbers, boolean[] used) {
    if (numbers.size() == 1) {
        double result = numbers.get(0) + EPSILON;
        if (Math.abs(result % 1) > 10 * EPSILON) return;
        int index = (int) (result + EPSILON);
        if (index >= 0 && index < used.length) used[index] = true;
        return;
    }

    List<Double> next;
    for (int i = 0; i < numbers.size(); i++) {
        for (int j = i + 1; j < numbers.size(); j++) {
            double a = numbers.get(i);
            double b = numbers.get(j);

            next = new ArrayList<>(numbers);
            next.remove(j);
            next.remove(i);

            next.add(a + b);
            eval(next, used);
            next.set(next.size() - 1, a - b);
            eval(next, used);
            next.set(next.size() - 1, b - a);
            eval(next, used);
            next.set(next.size() - 1, a * b);
            eval(next, used);
            if (b != 0) {
                next.set(next.size() - 1, a / b);
                eval(next, used);
            }
            if (a != 0) {
                next.set(next.size() - 1, b / a);
                eval(next, used);
            }
        }
    }
}

// Evaluate all expressions and count how many numbers from 1 to x can be expressed without any gaps
private static int getSequenceLength(List<Double> numbers) {
    boolean[] used = new boolean[1000];
    eval(numbers, used);

    int result = 0;
    while (used[result + 1]) result++;
    return result;
}

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);

    int numDigits = scanner.nextInt();
    List<Double> numbers = new ArrayList<>();
    for (int i = 0; i < numDigits; i++) {
        numbers.add(scanner.nextDouble());
    }

    System.out.println(getSequenceLength(numbers));

    scanner.close();
}

}