function sum (id, pr, n, a):
    a := array (n)
    count := 0
    i := 0
    j := 0
    k := 0
    for i := 0 until (n - 1):
        for j := (i + 1) until n:
            if (a[i] >= a[j]):
                k := a[j]
                a[j] := a[i]
                a[i] := k
    while (count < n & a[count] < 0):
        count += 1

    if (a[count] > 0):
        print(0)

    else:
        if (count == n):
            print(0)
        else:
            while ((a[count + 1] - a[count]) == 1 | (a[count + 1] == a[count])):
                count += 1
                if (count == n):
                    print(a[count - 1] + 1)
    print(a[count] + 1)