#include <iostream>

using namespace std;

int main()
{
  string input;
  cout << "Zadej cislo ve dvojkove soustave:" << endl;

  cin >> input;

  // go through input string from left to right
  for(int i = 0; i < input.size(); i++) {
    char ch = input[i];

    if(ch != '0' && ch != '1') {
      cout << "Nespravny vstup." << endl;

    }
  }