A traffic light at the turn for the “MEGA” shopping center from the Novomoskovskiy highway 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 mall to take a shopping, which results in a huge traffic jam at the turn. Administration of the mall ordered to install a camera at the nearby bridge, which is able to calculate the number of cars approaching this turn from the city. The observation started n minutes ago. You should use the data from the camera to determine the number of cars currently standing in the traffic jam.

The first line contains integers k and n (1 ≤ k, n ≤ 100), which are the number of cars that can take a turn to “MEGA” in one minute and the number of minutes passed from the beginning of observation. The second line contains space-separated integers a₁, …, a_n (0 ≤ a_i ≤ 100), where a_i 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 the number of cars currently standing in the traffic jam.