LZZY高级语言程序设计之写1+2+3+4+5+6+7+...+n

import java.util.Scanner;

public class MQ3 {
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in );
        System.out.println("请输入n的值");
        int a =sc.nextInt();

         System.out.println(a*1+a*(a-1)/2);  //运用等差数列的求和公式

    }
}
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