Water…
模拟…

#include <iostream>
using namespace std;
int main()
{
    int ans = 0;
    int ls = 0;

    int x;
    while(scanf("%d",&x) && x)
    {
        if(x == 1)
        ans += x,ls = x;
        else if(x == 2)
        {
            if(ls == 1)
            ans += 2,ls = 2;
            else 
            ans += ls+2,ls += 2;
        }
    }
    cout<<ans;
    return 0;
}