public static void main ( String [ ] args ) throws IOException {
  BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  PrintWriter pw = new PrintWriter ( System . out ) ;
  int t = 1 ;
  while ( t -- > 0 ) {
    int carry = 0 ;
    char a [ ] = br . readLine ( ) . trim ( ) . toCharArray ( ) ;
    long ans = 0 ;
    int n = a . length ;
    for ( int i = n - 1 ;
    i > 0 ;
    i -- ) {
      int val = Integer . parseInt ( "" + a [ i ] ) + carry ;
      if ( val == 2 ) {
        ans ++ ;
        carry = 1 ;
      }
      else if ( val == 1 ) {
        ans += 2 ;
        carry = 1 ;
      }
      else {
        ans ++ ;
      }
    }
    int val = Integer . parseInt ( "" + a [ 0 ] ) + carry ;
    if ( val == 2 ) ans ++ ;
    pw . println ( ans ) ;
  }
  pw . flush ( ) ;
}

public static void main ( String [ ] args ) throws IOException { BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ; PrintWriter pw = new PrintWriter ( System . out ) ; int t = 1 ; while ( t -- > 0 ) { int carry = 0 ; char a [ ] = br . readLine ( ) . trim ( ) . toCharArray ( ) ; long ans = 0 ; int n = a . length ; for ( int i = n - 1 ; i > 0 ; i -- ) { int val = Integer . parseInt ( " " + a [ i ] ) + carry ; if ( val == 2 ) { ans ++ ; carry = 1 ; } else if ( val == 1 ) { ans += 2 ; carry = 1 ; } else { ans ++ ; } } int val = Integer . parseInt ( " " + a [ 0 ] ) + carry ; if ( val == 2 ) ans ++ ; pw . println ( ans ) ; } pw . flush ( ) ; }
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