n,k=map(int,input().split())
L=[int(i) for i in list(input())]

def t(x):
	a=b=0
	for i in range(x):
		if a>0:a-=1
		else:b+=1
		a+=L[i%n]
	return(b,a)

if k<n:y=t(k)[0]
else:
	p,q=t(n)
	if p<q:y=p
	else:
		y=(p-q)*(k//n)+q+max(t(k%n)[0]-q,0)
	
print(y)