gistfile1.py

# Normal person mode
def next_server_number(l):
    if len(l) < 1:
        return 1
    for i in xrange(1, max(l)):
        if i not in l:
            return i
    return max(l) + 1
    
    
assert next_server_number([5, 3, 1]) == 2
assert next_server_number([5, 4, 1, 2]) == 3
assert next_server_number([3, 2, 1]) == 4
assert next_server_number([2, 3,]) == 1
assert next_server_number([2, 3]) == 1
assert next_server_number([]) == 1

# One liner
next_server_number = lambda l: next((x for x in xrange(1, max(l)) if x not in l), max(l) + 1) if len(l) > 0 else 1
assert next_server_number([5, 3, 1]) == 2
assert next_server_number([5, 4, 1, 2]) == 3
assert next_server_number([3, 2, 1]) == 4
assert next_server_number([2, 3,]) == 1
assert next_server_number([2, 3]) == 1
assert next_server_number([]) == 1