#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N = int(readline())
S = [int(x) % 2 for x in read().rstrip()]


def solve(S, N):
    ret = 0
    L = S.index(1)
    while N > L:
        N -= 1
        ret += 1
        S[N] ^= 1
    if S[N] == 1:
        if N == len(S) - 1:
            return 3
        S[N + 1] ^= 1
        S[N] = 0
        ret += 2
    if sum(S) == 0:
        return ret
    R = max(n for n, x in enumerate(S) if x == 1)
    while N < R:
        N += 1
        ret += 1
        S[N] ^= 1
        if S[N] == 1:
            if N + 1 == R:
                return ret + 2
            ret += 2
            S[N] = 0
            S[N + 1] ^= 1
    return ret


print(min(solve(S[:], N - 1), solve(S[::-1], len(S) - N)))