• 시간 제한 : 2초, 난이도 : 골드 2, 백준 1747번

import java.util.Scanner;
public class Practice39 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int[] A = new int[10000001];
		for(int i = 2; i < A.length; i++) {
			A[i] = i;
		}
		for(int i = 2; i < Math.sqrt(A.length); i++) {
			if(A[i] == 0) {
				continue;
			}
			for(int j = i + i; j < A.length; j = j + i) {
				A[j] = 0;
			}
		}
		int i = N;
		while(true) {
			if(A[i] != 0) {
				int result = A[i];
				if(isPalindrome(result)) {
					System.out.println(result);
					break;
				}
			}
			i++;
		}
		sc.close();
	}
	private static boolean isPalindrome(int target) {
		char temp[] = String.valueOf(target).toCharArray();
		int s = 0;
		int e = temp.length - 1;
		while(s < e) {
			if(temp[s] != temp[e])
				return false;
			s++;
			e--;
		}
		return true;
	}

}