The Berland Armed Forces System consists of n ranks that are numbered using natural numbers from 1 to n, where 1 is the lowest rank and n is the highest rank.

One needs exactly di years to rise from rank i to rank i + 1. Reaching a certain rank i having not reached all the previous i - 1 ranks is impossible.

Vasya has just reached a new rank of a, but he dreams of holding the rank of b. Find for how many more years Vasya should serve in the army until he can finally realize his dream.

Input

The first input line contains an integer n (2 ≤ n ≤ 100). The second line contains n - 1 integers di (1 ≤ di ≤ 100). The third input line contains two integers a and b (1 ≤ a < b ≤ n). The numbers on the lines are space-separated.

Output

Print the single number which is the number of years that Vasya needs to rise from rank a to rank b.

Examples

Input

3
5 6
1 2


Output

5


Input

3
5 6
1 3


Output

11
import java.io.*;
import java.util.*;
@SuppressWarnings("unused")
public class Main { //Название класса здесь
	private static boolean IOTypeIsFile = false; //Вид ввода/вывода. true-через файл. false-через консоль.
	private static String FileInput = ""; //Название файла ввода
	private static String FileOutput = "";//Название файла вывода
	private static Scanner in;
	private static PrintStream out,err;
	private static String ts(Object a) {return String.valueOf(a);}
	private static int ti(String a) {return Integer.valueOf(a);}
	private static double td(String a) {return Double.valueOf(a);}
	private static int[] arrayI(int n) {int[] ans = new int[n];
		for(int i = 0; i < n; ++i) {ans[i] = in.nextInt();}return ans;
	}
	private static String[] arrayS(int n) {String[] ans = new String[n];
		for(int i = 0; i < n; ++i) {ans[i] = in.next();}return ans;
	}
	private static double[] arrayD(int n) {double[] ans = new double[n];
		for(int i = 0; i < n; ++i) {ans[i] = in.nextDouble();}return ans;
	}
	private static void SomeVeryLargeUndUselessFunctionName() {if (!IOTypeIsFile) {err.print(FileInput+FileOutput);}}
	public static void main(String[] args) {
		err=new PrintStream(System.err);
		if(IOTypeIsFile) {
			File f = new File(FileInput);
			try {
				in = new Scanner(f);
				out = new PrintStream(FileOutput);
			} catch (FileNotFoundException var3) {System.err.println("404");}
		} else {
			in = new Scanner(System.in);
			out = new PrintStream(System.out);
		}
		run();
		in.close();
		out.close();
	}
	//Код пишут отсюда
	private static void run() {
		int n=in.nextInt(),ans=0;
		int[] d=arrayI(n-1);
		int a=in.nextInt()-1,b=in.nextInt()-1;
		for (int i=a;i<b;i++) {ans+=d[i];}
		out.println(ans);
	}
}