题解 | #【模板】静态区间和（前缀和）#

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int t = sc.nextInt();
        long[] a = new long[n + 1];
        long[] s= new long[n + 1];

        for(int i = 1; i <= n ; i ++){
            a[i] = sc.nextLong();
            s[i] = s[i - 1] + a[i];
        }

        while (t -- > 0){
            int l = sc.nextInt();
            int r = sc.nextInt();
            System.out.println(s[r] - s[l - 1]);
        }

        sc.close();
    }
}