#include <iostream>

#include <Windows.h>

#include <string>

using namespace std;

int main(void) {

    string str;

    int p = ; //记录当前二进制权重

    int s = ;

    cout << "请输入一个二进制数：";

    cin >> str;

    for (int i = str.length()-; i >= ; i--) {

        int x = str[i] - ''; // '0' - '0' = 0  '1' - '0' = 1

        s += x * p;

        p *= ; // p = p * 2

    }

    cout << s << endl;

    system("pause");

    return ;

}