#include<bits/stdc++.h>
using namespace std;
int main()
{
	int i,n,a,b,c,d;
	for(i=1000;i<=9999;i++){
		a=i/1000;
		b=i%1000/100;
		c=i%100/10;
		d=i%10;
		if(a==b&&c==d)
		cout<<i<<endl;
	}
	return 0;
}
/**************************************************************
	Problem: 1092
	User: houshanglin
	Language: C++
	Result: Wrong Answer
****************************************************************/