Problem: Ralph is in the Binary Country. The Binary Country consists of n cities and (n - 1) bidirectional roads connecting the cities. The roads are numbered from 1 to (n - 1), the i-th road connects the city labeled <image> (here ⌊ x⌋ denotes the x rounded down to the nearest integer) and the city labeled (i + 1), and the length of the i-th road is Li.

Now Ralph gives you m queries. In each query he tells you some city Ai and an integer Hi. He wants to make some tours starting from this city. He can choose any city in the Binary Country (including Ai) as the terminal city for a tour. He gains happiness (Hi - L) during a tour, where L is the distance between the city Ai and the terminal city.

Ralph is interested in tours from Ai in which he can gain positive happiness. For each query, compute the sum of happiness gains for all such tours.

Ralph will never take the same tour twice or more (in one query), he will never pass the same city twice or more in one tour.

Input

The first line contains two integers n and m (1 ≤ n ≤ 106, 1 ≤ m ≤ 105).

(n - 1) lines follow, each line contains one integer Li (1 ≤ Li ≤ 105), which denotes the length of the i-th road.

m lines follow, each line contains two integers Ai and Hi (1 ≤ Ai ≤ n, 0 ≤ Hi ≤ 107).

Output

Print m lines, on the i-th line print one integer — the answer for the i-th query.

Examples

Input

2 2
5
1 8
2 4


Output

11
4


Input

6 4
2
1
1
3
2
2 4
1 3
3 2
1 7


Output

11
6
3
28

Note

Here is the explanation for the second sample.

Ralph's first query is to start tours from city 2 and Hi equals to 4. Here are the options:

  * He can choose city 5 as his terminal city. Since the distance between city 5 and city 2 is 3, he can gain happiness 4 - 3 = 1. 
  * He can choose city 4 as his terminal city and gain happiness 3. 
  * He can choose city 1 as his terminal city and gain happiness 2. 
  * He can choose city 3 as his terminal city and gain happiness 1. 
  * Note that Ralph can choose city 2 as his terminal city and gain happiness 4. 
  * Ralph won't choose city 6 as his terminal city because the distance between city 6 and city 2 is 5, which leads to negative happiness for Ralph. 



So the answer for the first query is 1 + 3 + 2 + 1 + 4 = 11.

Solution (in JAVA):

Solution:

// Problem : D. Ralph And His Tour in Binary Country
// Contest : Codeforces - Codeforces Round #447 (Div. 2)
// URL : https://codeforces.com/contest/894/problem/D
// Memory Limit : 512 MB
// Time Limit : 2500 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

import java.io.*;
import java.util.*;
import java.util.stream.*;

public class a implements Runnable{
	
    public static void main(String[] args) {
        new Thread(null, new a(), "process", 1<<26).start();
    }
	public void run() {
		FastReader scan = new FastReader();
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
		//PrintWriter out = new PrintWriter("file.out");
		Task solver = new Task();
		//int t = scan.nextInt();
		int t = 1;
		for(int i = 1; i <= t; i++) solver.solve(i, scan, out);
		out.close();
	}

	static class Task {
		static final int inf = Integer.MAX_VALUE;

		public void solve(int testNumber, FastReader sc, PrintWriter pw) {
			//CHECK FOR QUICKSORT TLE
			//***********************//
			//CHECK FOR INT OVERFLOW
			//***********************//
			int n = sc.nextInt();
			int m = sc.nextInt();
			int[] wei = new int[n+1];
			for(int i = 1; i < n; i++) wei[i+1] = sc.nextInt();
			int[][] steg = new int[n + 2][];
			long[][] pref = new long[n + 2][];
			for(int i = n; i >= 1; i--) {
				int len = 0;
				if(i * 2 + 1 <= n) {
					len += steg[i*2+1].length + steg[i*2].length+1;
					steg[i] = new int[len];
					int ptr1 = 0;
					int ptr2 = 0;
					for(int j = 1; j < len; j++) {
						if(ptr1 < steg[i * 2].length && ((ptr2 >= steg[i*2+1].length || wei[i*2] + steg[i*2][ptr1] < wei[i*2+1] + steg[i*2+1][ptr2]))) {
							steg[i][j] = wei[i*2] + steg[i*2][ptr1++];
						}
						else {
							steg[i][j] = wei[i*2+1] + steg[i*2+1][ptr2++];
						}
					}
				}
				else if(i * 2 <= n) {
					len += steg[i*2].length + 1;
					steg[i] = new int[len];
					for(int j = 1; j < len; j++) {
						steg[i][j] = steg[2*i][j-1] + wei[i*2];
					}
				}
				else {
					len = 1;
					steg[i] = new int[1];
				}
				//System.out.println(Arrays.toString(steg[i]));
				pref[i] = new long[len];
				for(int k = 1; k < len; k++) {
					pref[i][k] = pref[i][k-1] + steg[i][k];
				}
			}
			for(int i = 0; i < m; i++) {
				int v = sc.nextInt();
				int h = sc.nextInt();
				long sum = 0;
				int l = 0; int r = steg[v].length - 1;
				while(r - l > 1) {
					int mid = (l + r) / 2;
					if(steg[v][mid] <= h) {
						l = mid;
					}
					else r = mid-1;
				}
				if(steg[v][r] < h) {
					l = r;
				}
				sum += 1l * h * (l + 1) - pref[v][l];
				h -= wei[v];
				//pw.println(sum + " " + l + " " + r);
				while(v > 1 && h > 0) {
					if((v ^ 1) <= n) {
						h -= wei[v ^ 1];
						l = 0; r = steg[v ^ 1].length - 1;
						while(r - l > 1) {
							int mid = (l + r) / 2;
							if(steg[v ^ 1][mid] <= h) {
								l = mid;
							}
							else r = mid-1;
						} 
						//pw.println(h + "zz" + " " + l + " " + r);
						if(steg[v ^ 1][r] < h) {
							l = r;
						}
						sum += Math.max(1l * h * (l + 1) - pref[v ^ 1][l], 0);
						h += wei[v ^ 1];
						v /= 2;
						sum += h;
						//pw.println(h + "ee");
						h -= wei[v];
					}
					else {
						v /= 2;
						sum += h;
						//pw.println(h + "ee");
						h -= wei[v];
					}
				}
				pw.println(sum);
			}
		}
	}
	static long binpow(long a, long b, long m) {
		a %= m;
		long res = 1;
		while (b > 0) {
			if ((b & 1) == 1)
				res = res * a % m;
			a = a * a % m;
			b >>= 1;
		}
		return res;
	}
	static void sort(int[] x){
		shuffle(x);
		Arrays.sort(x);
	}
	static void sort(long[] x){
		shuffle(x);
		Arrays.sort(x);
	}
	static class tup implements Comparable<tup>{
		int a, b;
		tup(int a,int b){
			this.a=a;
			this.b=b;
		}
		@Override
		public int compareTo(tup o){
			return Integer.compare(o.b,b);
		}
	}
	static void shuffle(int[] a) {
		Random get = new Random();
		for (int i = 0; i < a.length; i++) {
			int r = get.nextInt(i + 1);
			int temp = a[i];
			a[i] = a[r];
			a[r] = temp;
		}
	}

	static void shuffle(long[] a) {
		Random get = new Random();
		for (int i = 0; i < a.length; i++) {
			int r = get.nextInt(i + 1);
			long temp = a[i];
			a[i] = a[r];
			a[r] = temp;
		}
	}

	static class FastReader {
		BufferedReader br;
		StringTokenizer st;

		public FastReader() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		public FastReader(String s) throws FileNotFoundException {
			br = new BufferedReader(new FileReader(new File(s)));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	}

}