Is it possible "implement interface method in Abstract class"?

interface I1
    {
    int Add(int i1, int i2);
    }
public abstract class abstClass : I1
    {
    public int Add(int a, int b)
        {
        return a + b;
        }
    }
public class myClass : abstClass { }
    ...
    myClass mc = new myClass();
    Console.WriteLine(mc.Add(1, 2));

interface I1
    {
    int Add(int i1, int i2);
    }
public abstract class abstClass : I1
    {
    public abstract int Add(int a, int b);
    }
public class myClass : abstClass
    {
    public override int Add(int a, int b)
        {
        return a + b;
        }
    }
    ...
    myClass mc = new myClass();
    Console.WriteLine(mc.Add(1, 2));