Ambiguous interfaces

ambiguous.cs

public interface I1<U> 
{
  void M(U i); // generic first
  void M(int i);
}
public interface I2<U> 
{
  void M(int i);
  void M(U i); // generic second
}
public class C3: I1<int>, I2<int> 
{
  void I1<int>.M(int i) 
  {
    System.Console.WriteLine("c3 explicit I1 " + i);
  }
  void I2<int>.M(int i) 
  {
    System.Console.WriteLine("c3 explicit I2 " + i);
  }
  public void M(int i) 
  {
    System.Console.WriteLine("c3 class " + i);
  }
}
public class Test 
{
  public static void Main() 
  {
    C3 c3 = new C3();
    I1<int> i1_c3 = c3;
    I2<int> i2_c3 = c3;
    i1_c3.M(101);
    i2_c3.M(102);
  }
}