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## C. Turn for MEGA

Time limit: 1.0 second
Memory limit: 64 MB
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.

### Input

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, …, an (0 ≤ ai ≤ 100), 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

Output the number of cars currently standing in the traffic jam.

### Samples

inputoutput
```5 3
6 7 2
```
```0
```
```5 3
20 0 0
```
```5
```
Problem Author: Bulat Zaynullin
Problem Source: Ural Regional School Programming Contest 2010
To submit the solution for this problem go to the Problem set: 1787. Turn for MEGA