#include<iostream>
using namespace std;
int main(){
	int n[30],grade[30];
	int number=0;
	for(int i=0;i<30;++i){
		cin>>n[i];
		if(n[i]==1){
			grade[i]=1;
		}
		else if(n[i]==2&&i==0){
			grade[i]=2;
		}
		else if(n[i]==2&&i>0&&n[i-1]!=2){
			grade[i]=2;
		}
		else if(n[i]==2&&i>0&&n[i-1]==2){
			grade[i]=grade[i-1]+2;
		}
		number+=grade[i];
		if(n[i]==0){
			cout<<number<<endl;
			break;
		}
		else{
			continue;
		}
	}
	return 0;
}