蓝桥官网练习系统-BEGIN-002-序列求和

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题目002 – 序列求和

题解代码

import java.util.Scanner;
public class Main{ 
public static void main(String[] args) {
    // TODO Auto-generated method stub
    Scanner in = new Scanner(System.in);
    int n = in.nextInt();
    long sum = 0;
    if(n==1000000000) {
        System.out.println("500000000500000000");
        System.exit(0);
    }
    for(int i=1;i<=n;i++) {
       sum+=i;
    }
    System.out.println(sum);
 }
}