import java.util.Arrays;

public class Solution {
    public static int missingInteger(int[] a) {
        int min = 1;
        int[] sorted = Arrays.stream(a).distinct().sorted().toArray();

        for (int v : sorted) {
            if (v > 0) {
                if (min != v) {
                    break;
                }
                min++;
            }
        }

        return min;
    }
}