mport java.util.Scanner;

public class Main {
    public static double solution( int n ) {
        double ret = 0;
        for( int i = 2; i <= n; i++ ) {
            ret += temp( n, i ) * ( i - 1 );
        }
        return ret;
    }
    public static double temp( int n, int k ) {
        double m = 1;
        double t1 = n;
        for( int i = k; i > 0; i-- ) {
            m *= t1;
            t1--;
        }
        double o = 1;
        for( int i = k; i > 1; i-- ) {
            o *= i;
        }
        return ( m / o );
    }
    public static void main( String[] args ) {
        // TODO Auto-generated method stub
        Scanner sc = new Scanner( System.in );
        while( sc.hasNext() ) {
            int n = sc.nextInt();
            System.out.println((long)Main.solution( n ) );
        }
    }

}