A traffic light at the turn for the “Traffic Park” from M.G. Road works in such a way that k cars are able to take a turn in one minute. At weekends all the residents of the city drive to the Park to take a walk, which results in a huge traffic jam at the turn. The Traffic Officer Khandelwal, installed a camera at the nearby tower to help him monitor the traffic, which is able to calculate the number of cars approaching the turn for the park from the city. The observation started n minutes ago. Your task is to help Khandelwal figure out the number of cars currently stuck in the traffic jam with the help of the data provided from the camera.

Input:

The first line contains integers k and n which are the number of cars that can take a turn to Traffic park in one minute and the number of minutes passed from the beginning of observation. The second line contains space-separated integers a1, …, an where ai is the number of cars that approached the turn during the i-th minute. The observation started at morning, when there were no cars at the turn.

Output:

Help Officer Khandelwal figure out the number of cars currently stuck at the turn for traffic park.

Constraints

1 ≤ k, n ≤ 100
0 ≤ ai ≤ 100