import java.util.BitSet;
import java.util.NoSuchElementException;
import java.util.Scanner;

public class Main{

	static final Scanner s=new Scanner(System.in);

	public static void main(String args[]){
		int n=Math.max(s.nextInt()-101,3),res;
		PrimeIterator pri = new PrimeIterator(n+100);
		while((res=pri.next())<n);
		System.out.println(res+1);
	}
}
class PrimeIterator{

	private BitSet	bitSet;
	private int		nextV;
	private int		limit;

	public PrimeIterator(int limit){
		this.limit=limit;
		bitSet=new BitSet(limit+1);
		reset();
	}

	public boolean hasNext(){
		return nextV>=0;
	}

	public int next(){
		if(!hasNext())
			throw new NoSuchElementException();
		int r=nextV;
		for(int i=0; i<bitSet.size(); i+=nextV)
			bitSet.set(i);
		nextV=bitSet.nextClearBit(0);

		if(nextV>limit) nextV=-1;
		return r;
	}

	public void reset(){
		nextV=2;
		bitSet.clear();
		bitSet.set(0);
		bitSet.set(1);
	}
}