ZOJ 1712 Skew Binary

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

int main()
{
string a;
long num = 0;
int count = 1;
//    freopen("test.txt", "r", stdin);
while (cin >> a && a != "0")
{
for (int i = a.length() - 1; i >= 0; i--)
{
num += (a[i] - '0')* (pow ((double)2, count++) - 1 );
}
cout << num << endl;
num = 0;
count  = 1;
}

return 0;
}