随便写写

#include <iostream>
using namespace std;

int main(){

    int flag, prev = 0, ans = 0;

    while(cin >> flag, flag != 0){

        if (flag == 2) {
            if(prev == 1) prev = 0;
            prev += 2;
        } else prev = 1;

        ans += prev;
    }

    cout << ans;

    return 0;
}