Codeforces 문제 푸는 길 - 546A Soldier and Banas

1562 단어 Codeforces
A. Soldier and Bananas
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
A soldier wants to buy w bananas in the shop. He has to pay k dollars for the first banana, 2k dollars for the second one and so on (in other words, he has to pay i·k dollars for the i-th banana).
He has n dollars. How many dollars does he have to borrow from his friend soldier to buy w bananas?
Input
The first line contains three positive integers k, n, w (1  ≤  k, w  ≤  1000, 0 ≤ n ≤ 109), the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.
Output
Output one integer — the amount of dollars that the soldier must borrow from his friend. If he doesn't have to borrow money, output 0.
Examples
input
3 17 4

output
13

제목: 병사가 w개의 바나나스를 사려고 하는데 주머니에 n이 들어있어요. 첫 번째 바나나k, 두 번째 바나나2k에 따라...친구에게 얼마를 빌려달라고 부탁했다.
문제풀이 사고방식: 물문제, 사고방식이 필요 없어요.
다음은 문제풀이 코드(java 구현)
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scanner = new Scanner(System.in);
		int k = scanner.nextInt();
		int n = scanner.nextInt();
		int w = scanner.nextInt();
		
		int sum = 0;
		for(int i = 1;i <= w;i++){
			sum += i*k;
		}
		if(sum > n){
			System.out.println(sum-n);
		}else{
			System.out.println(0);
		}
		scanner.close();		
	}	
}

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