等差数列： 以k为首相，k为公差，w个数量的和与n的大小关系 输出max(sum-0,0)

Java程序

 

import java.util.Scanner;public class A546 {    static void run(){        Scanner in = new Scanner(System.in);        int k =in.nextInt();        int n = in.nextInt();        int w = in.nextInt();        int count = 0;        count = (1+w)*w*k/2;//        System.out.println(count);        if(count>n){            System.out.println(count-n);        }else            System.out.println(0);    }    public static void main(String[] args){        run();    }}

Python程序

def A546():    k,n,w = map(int, raw_input().split())    count = (1+w)*w*k*0.5    if count > n :        print int(count -n)     else:        print 0 if __name__=='__main__':    A546()