#include <iostream>
#include <bitset>

const int size_int = sizeof(int)*8; // 8 bita po byte-u

using namespace std;

bool check(const   bitset<size_int>&  bin , int count)
{
  if(bin[0] == 1)
  return false;

  for(int i=0 ; i<count ; i++)
  {
      if( bin[i] == 0)
      continue;
      
      else 
      {
        for(int j= i ; j<count ; j++)
        {
             if(bin[j] != 1)
             return false;
 
            else
            continue;
         }
      }
  }
  return true;
}

int main ()
{
  string binary;
  cout << "upisi binarni broj : ";
  cin >> binary;

  bitset<size_int> bitNumber (binary);

  cout<< endl << "rezultat : " << boolalpha 
      <<check(bitNumber , binary.size() ) << endl;

  return 0;
}