def calc(max_shyness, data_list):
    if max_shyness == 0:
        return 0
    else:
        total_count, required_count = 0, 0
        for i in range(0, max_shyness+1):
            if data_list[i] != 0:
                if total_count >= i:
                    total_count += data_list[i]
                else:
                    diff = i - total_count
                    required_count += diff
                    total_count = total_count + diff + data_list[i]
        return required_count

def calc_required_number(data):
    if len(data) == 1:
        return -1
    if len(data) == 2:
        max_shyness, data_list = data[0], data[1]
        return calc(int(max_shyness), list(map(int, data_list)))

try:
    with open('a-large-practice.txt') as datasets:
        count = 0
        for line in datasets:
            res = calc_required_number((line.rstrip()).split(' '))
            if res != -1:
                print("Case #"+str(count)+": " + str(res))
            count += 1
except IOError as err:
    print('File error: ' + str(err))