The Priest Mathematician

http://acm.hust.edu.cn/vjudge/contest/view.action?cid=31329#problem/F

f[0] = 1 , f[ i ] = f[ i - 1 ] + 2 ^( n - k - 2 )

 

import java.util.Scanner;

import java.math.BigInteger ;

public class Main

{

	public static void main(String[] args )

	{

		Scanner cin = new Scanner( System.in );

		BigInteger[] f = new BigInteger[ 10005 ] ;

		int k = 1 , cnt = 0 ;

		f[ 0 ] = new BigInteger( "0" ) ;

		BigInteger d = new BigInteger( "1" ) ;

		for( int i = 1;  i <= 10004 ; ++i )

		{

			f[ i ] = f[ i - 1 ].add( d ) ;

			cnt++;

			if( cnt == k )

			{

				cnt = 0 ;

				k++;

				d = d.multiply(BigInteger.valueOf(2) ) ;

			}

		}

		while( cin.hasNext())

		{

			int n = cin.nextInt();

			System.out.println( f[ n ] ) ;

		}

	}

}