暴力枚举

import java.util.Random;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            int num = sc.nextInt();
            int ans;
            String str = Integer.toString(num);
            int x = (int)(Math.sqrt(num));
            if(num == 1) System.out.println(1);
            else {
                if(x * x == num){
                    System.out.println(0);
                }else {
                    boolean flag = true;
                    while (x > 0){
                        int l = 0;//双指针
                        int r = 0;
                        flag = true;
                        String a1 = Integer.toString(--x * x);
                        while(r < a1.length()){
                            if(l >= str.length()){
                                flag = false;
                                break;
                            }
                            if(str.charAt(l) == a1.charAt(r)){
                                l++;
                                r++;
                            }else {
                                l++;
                            }
                        }
                        if(flag) {
                            break;
                        }
                    }
                    String s = Integer.toString(x * x);
                    ans = str.length() - s.length();
                    if(flag){
                        if(x == 0) System.out.println(-1);
                        else System.out.println(ans);
                    }
                    else System.out.println(-1);
                }
        }
    }
}