#include<iostream>

using namespace std;

int main()
{
    int i,sum = 0;
    int st;
    int k = 1;
    while(cin>>i,i)
    {
        if(i==1)
        {
            sum++;
            st = true;
        }
        else if(i==2)
        {
            if(st) 
            {
                k = 1;
                st = false;
            }
            sum = sum+2*k;
            k++;
        }
    }
    cout<<sum;
    return 0;
}