n,k=map(int,input().split())
s=input()

u=max(len(s)-sum(map(int,s)),0)

cost=k//n*u
prize=0
for c in s[:k%n]:
    if prize>0: prize-=1
    else:       cost+=1
    if c!="0":  prize+=int(c)

print(max(cost,1))