import java.io.*;
public class KeyboardTest{
	public static void main(String args[]){
		System.out.println("This is a example about keyboard inputting.");
		String strObj = "0";
		try
		{
			InputStreamReader inObj;
			BufferedReader bufObj;
			inObj = new InputStreamReader(System.in);
			bufObj   = new BufferedReader(inObj);
			strObj = bufObj.readLine();
			System.out.println("輸入的整數N為:  "+strObj);
		}catch(IOException e){
			System.out.println("Exception:  "+e);
		}
		int n = Integer.parseInt(strObj);
		int multiNum;
		multiNum = n*(n+1)/2;
		System.out.println("1到N的和為:  "+multiNum);
	}
}