#include<iostream>
using namespace std;

int n;
string s;

int solve()
{
    int cnt = 0;
    cin>>n;
    cin>>s;
    for(int i=0;i<n;i++)
    {
        if(s[i] == '1')
        {
            if(s[i] != s[i-1]) cnt++;
        }
    }
    if(s[n-1] == '1') cnt--;
    return cnt;
}

int main()
{
    freopen("freddy.in", "r", stdin);
    freopen("freddy.out", "w", stdout);
    cout<<solve()<<endl;
	return 0;
}