CCF 201803-1 跳一跳

#include <iostream>
//#include <bits/stdc++.h>
#include <string>

using namespace std;

int main()
{
    int number;
    int sum=0;
    int base=2;
    bool flag=false;
    while(cin>>number)
    {
        if(number==0)
        {
            cout<<sum;
            return 0;
        }
        else if(number==1)
        {
            sum++;
            flag=false;
            base=2;
        }
        else if(number==2)
        {
            flag=true;
            sum+=base;
            if(flag==true)
                base+=2;
        }
    }
    cout<<sum;
    return 0;
}