text: /*
  ************************************************
  username    :   smmehrab
  fullname    :   s.m.mehrabul islam
  email       :   mehrab.24csedu.001@gmail.com
  institute   :   university of dhaka, bangladesh
  session     :   2017-2018
  ************************************************
  */
  #include<stdio.h>
  
  int main()
  {
      unsigned long long int n,c=0;
      scanf("%llu",&n);
      
      while(n!=0)
      {
  		n/=2;
  		c++;
      }
  	printf("%llu\n",c-1);
  	return 0;
  
  }
  