#define _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"
using namespace std;
#define rep(i, n) for(int i=0; i<(n); ++i)
#define FOR(i, m, n) for(int i=(m); i<(n); ++i)
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
#define mp make_pair
#define pb push_back
#define Cout(x) cout << (x) << endl
#define Cout2(x, y) cout << (x) << " " << (y) << endl
#define dump(x) cerr << #x << " = " << (x) << endl;
typedef long long LL;
typedef vector<int> VI;
typedef vector<LL> VL;
typedef vector<string> VS;
typedef vector<bool> VB;
typedef vector<vector<int>> VVI;
typedef pair<int, int> PII;
const int inf = 1e9;
const double pi = acos(-1.0);

bool PalinCheck(string s) {
	bool ret = true;
	int size = (int)s.size();
	for (int i = 0; i < size / 2; ++i) {
		if (s[i] != s[size - i - 1]) {
			ret = false;
			break;
		}
	}
	return ret;
}

int main() {
	int n; cin >> n;
	VI can;

	for (int i = n; i >= 0; i--) {
		if (PalinCheck(to_string(i))) {
			can.pb(i); break;
		}
	}
	for (int i = n + 1; true; i++) {
		if (PalinCheck(to_string(i))) {
			can.pb(i); break;
		}
	}

	int ans = 0, mi = inf;
	for (auto aa : can) {
		if (mi > abs(aa - n)) {
			ans = aa;
			mi = abs(aa - n);
		}
	}
	Cout(ans);
}
