Jumping on the Clouds: Revisited

n,k=map(int,input().split())
cloud=list(map(int,input().split()))
energy=100
count=0
i=0
while(i!=len(cloud)):
    if(cloud[i]==1):
        count=energy-3
        energy=count
    else:
        count=energy-1
        
    i+=k
print(count)