#include<bits/stdc++.h>
#define Yukinoshita namespace
#define Yukino std
#define int long long
using Yukinoshita Yukino;
int read()
{
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9') w=ch=='-'?-1:1,ch=getchar();
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
char s[100005];
signed main()
{
	int n=read(),i,cnt=0,sum=0;
	scanf("%s",s+1);
	for(i=1;i<=n;i++)
		if(s[i]=='1')
			sum++,cnt=2;
		else if(cnt)
			sum++,cnt--;
	cout<<sum;
}