import java.util.ArrayList;

import java.util.Arrays;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

public class BinaryGap {

public static void main(String[] args) {

String binary = Integer.toBinaryString(15);

char[] binaryArr = binary.toCharArray();

List<Integer> gaps = new ArrayList<>();

int count = 0;

for(int i = 0; i < binaryArr.length; i++) {

if(i+1 < binaryArr.length) {

if(binaryArr[i] == '1' && binaryArr[i+1] == '0') {

count++;

}

if(binaryArr[i] == '0' && binaryArr[i+1] == '0') {

count++;

}

if(binaryArr[i] == '0' && binaryArr[i+1] == '1') {

gaps.add(count);

count = 0;

}

}

}

System.out.println(gaps.stream().max(Integer::compare).orElse(0));

}

}