#include <bits/stdc++.h>

#define int long long

#define double long double

#define INF (int)(1e18)

#define maxn 500005

using namespace std;

string s;

int sta[maxn];

int cnt = 0;

signed main() {
	
	ios::sync_with_stdio(0);
	
	cin.tie(0);
	
	cout.tie(0);
	
	cin >> s;
	
	for(int i = 0;i < (int)s.length();++ i){
		
		sta[++ cnt] = i;
		
		while(cnt >= 2 && s[sta[cnt]] == s[sta[cnt - 1]]){
			
			cnt -= 2;
			
		}
		
	}
	
	cout << s;
	
	int top = sta[cnt];
	
	top = min(top,(int)(s.length()) - 2);
	
	for(int i = top;i >= 0;-- i) cout << s[i];
	
	return 0;
	
}
/*
ABBCDDE
ABBCDDEDDCBBA
*/