N,K = map(int,input().split())
S = list(input())
temp = 0
for i in range(N):
    if S[i]=='2':
        S[i]='1'
        temp+=1
    elif S[i]=='0' and temp>0:
        S[i]='1'
        temp-=1
if K==1:
    print(1)
elif N==1:
    if S[0]=='0':
        print(K)
    else:
        print(1)
elif N<K:
    ans=1
    ans+=S.count('0')
    for i in range(N):
        if S[i]=='0' and temp>0:
            S[i]='1'
            temp-=1
    K-=N+1
    ans+=(K//N)*S.count('0')
    if K%N>0:
        ans+=S[:K%N].count('0')
    print(ans)
else:
    print(1+S[:K-1].count('0'))