#include<bits/stdc++.h>
using namespace std;

map<string, int>mp;
int id = 1;
map<int, string>src;

void deal(string &s)
{
	for(auto &it : s)
	{
		if(it == '!')
			it = ' ';
	}	
}

string convert(string t)
{
	string s = t;
	for(auto &it : s)
		if(it >= 'A' && it <= 'Z')
			it = it - 'A' + 'a';
	return s;
}

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);

	string s; cin >> s;
	deal(s);
	
	vector<int>v; v.clear();
	stringstream is(s);
	
	auto print = [&]()
	{
		cout << src[v[0]];
		for(int i = 1; i <v.size(); i++)
			cout << "!" << src[v[i]];
		cout << endl;
	};

	string t;
	while(is >> t)
	{
		string str = convert(t);

		if(!mp.count(str)) {
			src[id] = t;
			mp[str] = id++;
		}
		v.push_back(mp[str]);
	}

	int n = v.size();
	while(1)
	{
		int len = 1, loc = -1;
		for(int i = 0; i < n - 1; i++)
		{
			int sum = 1, cnt;
			if(v[i] == v[i + 1]) {
				for(cnt = 0; i - cnt >= 0 && i + cnt + 1 < n - 1; cnt++)
					if(v[i - cnt] != v[i + cnt + 1])
						break;
				sum = max(cnt * 2, sum);	
			}

			else {
				for(cnt = 1; i - cnt >= 0 && i + cnt < n - 1; cnt++)
					if(v[cnt + i] != v[i - cnt])
						break;
				sum = max(sum, cnt * 2 - 1);
			}

			if(sum > len) {
				len = sum;
				loc = i;
			}
		}

		// cout << len << " " << loc << endl;
		if(loc == -1)break;

		int st, ed;
		if(v[loc] == v[loc + 1]) {
			st = loc - len/2 + 2;
			ed = loc + len/2 + 1;
		}
		
		else {
			st = loc - len / 2 + 1;
			ed = loc + len / 2 + 1;
		}

		v.erase(v.begin() + st, v.begin() + ed);
		n = v.size();
		// print();
	}

	print();
	
	return 0;
}