题解 | #【模板】前缀和#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
            int n = in.nextInt();
            int q = in.nextInt();
            long[] arr = new long[n];
            arr[0] = in.nextLong();
            for (int i = 1; i < n; i++) {
                arr[i] = arr[i-1] + in.nextLong();
            }
            for (int i = 0; i < q; i++) {
                int a = in.nextInt();
                int b = in.nextInt();
                if (a-2 >= 0) {
                    System.out.println(arr[b-1] - arr[a-2]);
                } 
                else {
                    System.out.println(arr[b-1]);
                }
                
            }
        
    }
}