#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (a) - 1; i >= (b); i--)
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long LL;
typedef vector<int> VI;
typedef vector<LL> VL;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef double db;

void solve()
{
	string s;
	cin >> s;
	if (*min_element(ALL(s)) == *max_element(ALL(s)))
		cout << s[0] << '\n';
	else
	{
		int x = s[0] - '0';
		if (s[0] == s.back())
			cout << x << 1 - x << x << '\n';
		else
			cout << x << 1 - x << '\n';
	}
}


int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	int t = 1;
	while(t--)
		solve();
	
	return 0;
}