n=int(input())
s=input()
ans=10**10
zero=s.count("0")
one=n-zero
if zero==0 or zero==n:
  exit(print(0))
se=set()
if s[0]=="1":
  se.add(0)
  for i in range(n-1,-1,-1):
    if s[i]=="1":
      se.add(i)
    else:break
for l in range(n):
  a=list(range(l+n,l+one+n))
  sp_l=(l+one)%n
  sp_r=n
  if sp_l==0:sp_r=0
  for ll in range(n*3):
    b=[]
    for i in range(ll,ll+n):
      if s[i%n]=="1":b.append(i)
    #print(b,a)
    ansl=0
    ansr=0
    if b[0]<=a[0]:
      if sp_l<=((b[0]-1)%n+1)<=sp_r and (b[0]%n not in se):
        ansl=a[0]-b[0]-1
      else:
        ansl=a[0]-b[0]
    for i in range(one):
      if b[i]>a[i]:
        ansr+=1
    ans=min(ans,max(ansl,ansr)*n+(-l-one)%n)
print(ans)