n,k = map(int,input().split(" "))
x = k
list1 = list(map(int,input().split(" ")))
final_list1 = []
for i in list1:
    l1 = [i for i in range(1,i+1)]
    l2 = []
    while len(l1) != 0:
        l2.append(l1[:x])
        l1 = l1[x:]
        x = min(k,len(l1))
    final_list1.extend(l2)
final_list2 = [i for i in final_list1 if len(i) != 0]
count = len([final_list2[i-1] for i in range(1,len(final_list2)+1) if i in final_list2[i-1]])
print(count)``