NYOJ题目436sum of all integer numbers

 1 import java.io.BufferedReader;
 2 import java.io.IOException;
 3 import java.io.InputStreamReader;
 4 
 5 public class Main {
 6 
 7     public static void main(String[] args) throws NumberFormatException, IOException {
 8         
 9         BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
10         
11         boolean first=true;
12         while(first || reader.ready()){
13             first=false;
14             
15             int n=Integer.parseInt(reader.readLine());
16             long ans=n;
17             if(n>0){
18                 while(--n>=1) ans+=n;
19             }else{
20                 while(++n<=1) ans+=n;
21             }
22             System.out.println(ans);
23         }
24         
25     }
26     
27 }