题目1506：求1+2+3+...+n

import java.util.Scanner;import java.io.FileReader;import java.io.IOException;class Main{public static final boolean DEBUG = false;public static int dfs(int n){if (n == 1) return 1;else return n + dfs(n - 1);}public static void main(String[] args) throws IOException{Scanner cin;int n;if (DEBUG) {cin = new Scanner(new FileReader("d:\\OJ\\uva_in.txt"));} else {cin = new Scanner(System.in);}while (cin.hasNext()) {n = cin.nextInt();System.out.println(dfs(n));}}}