package no312; import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); long n = sc.nextLong(); n = 499999999979L * 2; //3以上の最小の約数 long max = (long) Math.sqrt(n); for(long i=3;i<=max;i++) { if (n % i == 0) { System.out.println(i); return; } } if (n % 2 == 0) { System.out.println(n / 2); return; } System.out.println(n); } }