n = int(input())
s = input()
zeros = s.count('0')

if not zeros or zeros == n:
    print(0)
    exit()

ans = n * n
l = [0, 0]

if s[0] != '0':
    for c in s[1:]:
        if c != '0':
            break
        l[1] += 1
else:
    l[0] += 1
    for c in s[1:]:
        if c != '0':
            break
        l[0] += 1

for i, c in enumerate(reversed(s)):
    ans = min(ans, i + n * (zeros - l[0]))
    if c != '0':
        l[1] = l[0]
        if l[0]:
            l[0] = 1
    else:
        l[0] += 1
        l[1] += 1
        ans = min(ans, i + n * max(1, zeros - l[1]))

print(ans)