n = int(input())
place = int(input())
lst = [ ]
count = 0
for i in range(place):
    ele = int(input())
    lst.append(ele)
for i in range(place):
    if lst[i] == 1:
        count += 1
        for j in range(n):
            if i + j > place:
                break
print(lst.count(1))