最长方连续方波信号

while True:
    try:
        signals = input()
        if "010" not in signals:
            print(-1)
            break
        sign = "010"
        for i in range(len(signals)):
            if sign + "11" in signals and sign + "10" not in signals:
                prinf(sign)
                break
            else:
                if sign in signals:
                    sign += "10"
                else:
                    print(sign[:-2])
                    break
    except:
        break

// 只完成190

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        int n = s.length();
        s+="0";
        String ans="";
        int be=0;
        while(be<n && s.charAt(be)=='1') be++;
        if(be>=n){
            System.out.println(-1);
            return;
        }
        for(int i=0; i<n; i++){
            if(s.charAt(i)=='0'&&s.charAt(i+1)=='0'){
                if(i!=be && (i-be+1)%2==1){
                    int t=0;
                    boolean flag = true;
                    for(int j=be; j<=i;j++){
                        if(s.charAt(j)-'0'!=t){
                            flag = false;
                            break;
                        }
                        t=(t+1)%2;
                    }
                    if(flag){
                        if(ans.length()<(i-be+1))
                            ans=s.substring(be,i+1);
                    }
                }
                be=i+1;
            }
        }
        if(ans.length()>0) System.out.println(ans);
        else System.out.println(-1);
    }
}

// 满分