/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes hereint a[]
		int[]a = {1,2,3,4,5,6};
		int[]prefix = new int[a.length+1];
		Arrays.fill(prefix,0);
		for(int i = 1;i<=a.length;i++){
			prefix[i] = prefix[i-1]+a[i-1];
		}
		System.out.println(findSumInRange(prefix,2,4));
	}
	static int findSumInRange(int [] prefix ,int l, int r){
 
		return prefix[r]-prefix[l-1];
	}
}

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