/* 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
	{
		String[] num = {"7","16","55","4","10"};
 
     	System.out.println(getSum(2, 2, num));
     	System.out.println(getSum(3, 2, num));
 
	}
 
	private static int getSum(int N, int M, String[] num) {
		int count = 0, sum = 0;
		for (int i = 0; i < num.length && count < N; i += M) {
	    	sum = sum + Integer.parseInt(num[i]);
	    	count++;
	    }
	    return sum;
	}
}

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