Pro1

原始文件为 CPP 代码，本文是转换后的 Markdown 文件。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <string>

using namespace std;

int main()
{
    freopen("in.txt","r",stdin);
    int n;
    int ans = 0;
    int prev = 0;

    while(true)
    {
        scanf("%d",&n);
        if(n == 0) break;   
        else if (n == 1)
        {
            ++ans; prev = 0;
        }
        else if (n == 2)
        {
            prev = prev + 2;
            ans = ans + prev;
        }
    }   

    printf("%d\n",ans);
}