#include<bits/stdc++.h>
#include<iostream>
using namespace std;
typedef long long ll;
ll n,a[10001],l,r;
bool b;
inline ll read(){
	ll k=0;char ch=getchar();
	while(!isdigit(ch))ch=getchar();
	while(isdigit(ch))k=(k<<1)+(k<<3)+(ch^48),ch=getchar();
	return k;
}
int main(){
	n=read();
	for(ll i=1;i<=n;i++){
		a[i]=read();
		if(a[i]==1){
			if(l==0)l=i;
			else r=i;
			b=1;
		}
	}
	if(b==0)cout<<0;
	else if(l==r||r==0)cout<<1;
	else cout<<r-l+1;
	return 0;
}