/* 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
	{
		
	}
	
		public abstract class MetricFunction<T extends MetricFunction> {
	
		    public abstract double NDerv(int dervIndex, List<Double> evalPoint);
		
		}
	
		public static class NumericMetricFunction extends MetricFunction {

		    public double NDerv(int dervIndex, List<Double> evalPoint) {
		
		        //Do something...
		        double answer = 0.;
		
		        return answer;
		    }
		}
}