k값을 3으로 명시적으로 적어도 원래 오답인가요? ㅠㅠ

import java.util.*;

public class Main {
	public int solution(int n, int m, int[] a) {
		int answer = 0, sum = 0;
//		int max = Integer.MIN_VALUE;
		for (int i = 0; i < 3; i++) {
			sum += a[i];
		}
		answer = sum;
		for(int i = m; i < n; i++) {
			sum += (a[i] - a[i-3]);
			answer = Math.max(answer, sum);
		}
		return answer;
	}

	public static void main(String[] args) {
		Main T = new Main();
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int m = scan.nextInt();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = scan.nextInt();
		}
		System.out.println(T.solution(n, m, arr));

	}
}