import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int ans = 0;
        int pre = 1;//上一次的得分
        int type = in.nextInt();//跳跃的类型
        while ( type != 0 ) {
            if ( type == 1 ) {//不为中心
                pre = 1;
                ans += 1;
            } else {
                if ( pre == 1 ) {//上一次不是中心
                    pre = 2;
                    ans += pre;
                } else {
                    pre += 2;
                    ans += pre;
                }
            }
            type = in.nextInt();
        }
        System.out.println(ans);
    }

}