C/C++ :: Incorrect Output From Unsigned Binary To Decimal Program

This program has to convert an unsigned binary number into a decimal number. No matter what binary number I enter, however, it always outputs that the decimal number is 0.

My code is as follows:

#include <iostream>
#include <cmath>
#include <algorithm>
using namespace std;
int main() {
string binarynumber;
cout << "Enter an unsigned binary number up to 32 bits." << endl;

[Code] ....

And my output:

Enter an unsigned binary number up to 32 bits.
00001111
That number in decimal is 0

The output should have shown the binary number in decimal to be 15, and I cannot find my error.