use proconio::{input, marker::Chars};

fn main() {
    input! {
        n: usize,
        mut s: Chars,
    }

    if n == 1 && s[0] == '0' {
        println!("1");
        return;
    }

    s.splice(0 .. 0, ['1', '1', '1']);

    let mut ans = 0;
    for i in 2 .. s.len() {
        if &s[i - 1 ..= i] == &['0', '0'] {
            s[i] = '0';
            ans += 1;
        }
        if &s[i - 2 .. i] == &['0', '1', '0'] {
            s[i] = '1';
            ans += 1;
        }
    }

    println!("{ans}");
}