# O(N^3)
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_l=n
  #print(sp_l,sp_r)
  for ll in range(n*3):
    b=[]
    for i in range(ll,ll+n):
      if s[i%n]=="1":b.append(i)
    ansl=0
    ansr=0
    flag=True
    flagg=False
    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
        x=a[i]
        if x%n:x+=n-(x%n)
        if x<a[-1]:
          if a[i]<=b[i]<=x:
            flagg=True
          x+=n
        if a[i]<=b[i]<=x:
          flag=False
    if ansr:ansr+=flag
    ansr-=flagg
    #print(l,ll,"---",max(ansl,ansr)*n+(-l-one)%n,sp_l<=((b[0]-1)%n+1)<=sp_r and (b[0]%n not in se),flag)
    #print(ansl,ansr)
    #print(b,a)
    ans=min(ans,max(ansl,ansr)*n+(-l-one)%n)
print(ans)