01交错数列

import java.util.*;
public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        List<Integer> v = new ArrayList<>();
        for(int i = 0; i < a; ++i) v.add(sc.nextInt());
        if(v.size() <= 1){     //长度小于等于1直接返回
            System.out.println(v.size());
            return;
        }
        if(v.indexOf(0) == -1 || v.indexOf(1) == -1){  //只含0或1直接返回
            System.out.println(1);
            return;
        }
        int pre = v.get(0), r = 1;    //用pre记录前一个数字
        for(int i = 1; i < v.size(); ++i){
            if(v.get(i) + pre == 1){  //当前数字与pre不同，长度加一
                r++;
                pre = 1 - pre;        //更新pre
            }
        }
        System.out.println(r);
    }
}