#include<bits/stdc++.h>
using namespace std;
int main() {
    int g,s,b,q;
    for(int i=1000;i<=9999;i++){
        g=i%10;
		s=i/10%10;
		b=i/100%10;
		q=i/1000;
		if(g==s&&b==q) cout<<i<<endl;	
    }
}
/**************************************************************
	Problem: 1092
	User: wangyiyang
	Language: C++
	Result: Wrong Answer
****************************************************************/