#yuki_78

n,k=map(int,raw_input().split())
s=raw_input()
res=0
point=cost=0
if k>=n:
 for i in xrange(n):
  if point==0:
   cost+=1
  else:
   point-=1
  point+=int(s[i])
 res+=cost
 k=k-n
 res+=k/n*max(cost-point,0)

cost2=0
point2=point
for i in xrange(k%n):
 if point2==0:
  cost2+=1
 else:
  point2-=1
 point2+=int(s[i])
res+=cost2
print res