k, n = [int(x) for x in input().split()]
a = list(map(int, input().split()))
m = 0

for i in a:
    m += i
    if (m - k >= 0):
        m -= k
    else:
        m = 0
print(m)

explain please. for whar we need n then?

try this example:
4 3
1 5 6
You cannot pass the sixth test. In the first minute there are 0 cars left. In the second minute there was 1 car left. At the third minute there were 2+1 cars left.
Read the conditions of the task more carefully. ))))