# ZeroJudge - b562: 2.神奇的「負二進位表示法」
### 題目連結：https://zerojudge.tw/ShowProblem?problemid=b562
###### tags: `ZeroJudge` `模擬`

#include <iostream>
#include <string>
using namespace std;

static const auto Initialize = [] {
	cin.sync_with_stdio(false); cin.tie(nullptr);
	return nullptr;
}();

int main() {
	int decimal;
	string binary;
	while (cin >> binary) {
		decimal = 0;
		for (int i = 0; i != binary.size(); ++i)
			if (binary[i] == '1') {
				if ((binary.size() - i) & 1)
					decimal += (1 << (binary.size() - i - 1));
				else
					decimal -= (1 << (binary.size() - i - 1));
			}
		cout << decimal << '\n';
	}
}