#include <bits/stdc++.h>
using namespace std;
int main() {
	long long n, d = 0, p, p2, q;
	cin >> n;
	for (long long i = 0; i < n; i++) {
		cin >> p2;
		q = p2;
		p = 0;
		while (p2) {
			p = p * 10 + p2 % 10;
			p2 /= 10;
		}
		if (q == p && d < p) {
			d = p;
		}
	}
	cout << d;
	return 0;
}