import java.*;
import java.math.*;
import java.util.*;
/**
*
* @author tiirz
*/
public class Main {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
Scanner in=new Scanner(System.in);
BigInteger m;
int n;
n=2;
BigInteger a = BigInteger.valueOf(2);
n=in.nextInt();
BifInteger g=a.multiply(a.add(BigInteger.valueOf(1))).divide(BigInteger.valueOf(2));
System.out.println(m);
}
}
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