#include <iostream>
using namespace std;
int main() {
	int n, heso, tong = 0, nhan;
	cout << "Nhap so nhi phan: ";
	cin >> n;
	for (int i = 0; n != 0;i++) {
		heso = n % 10;
		if (heso != 0 && heso != 1) {
			cout << "Nhap sai so.";
			tong = 0;
			break;
		}
		if (heso != 0) {
			nhan = pow(2, i);
			tong += nhan;
		}
		n = n / 10;
	}
	if (tong != 0) {
		cout << "Thap phan la: " << tong;
	}
}