import java.util.Scanner;
public class ErFenSearch{
public static void main(String[]args){
Scanner sc=new Scanner(System.in);
//二分查找
int []arr=new int[]{12,14,25,64,75,89,99,101}; //顺序数组
int desc=sc.nextInt();//输入要查找的数字；
int left=0,right=arr.length-1;
boolean loop=false;
//判断是否存在元素
while(left<=right){
int mid=(left+right)/2;//定义数组中间的下标:
if(desc>arr[mid]){
left=mid+1;//左边下标向右边移动
}else if(desc<arr[mid]){
right=mid-1;//右边下标向左边移动
}else if(desc==arr[mid]){//单找的数与中间值相同
System.out.println("存在:"+arr[mid]);
loop=true;
break;
}
}
if(loop==false){
System.out.println("不存在");
}
}
}