A friend of mine gave me this problem. It goes like this.
In a normal game of chess, the white player checks the black's king with a rook and a bishop as in the following image.
8/8/8/8/8/7k/8/3K1B1R b - - 0 1
Now the image seems a bit awkward. In the last move before the check, the white player will have moved either his rook or his bishop (but not both). Suppose that in the last move the white rook is moved, so the black king and white bishop would already be at the same position as they are now. So the black king was already checked by the bishop and hence it was impossible for the black king to remain in that position. Similarly, if the white bishop is moved in the last move, the black king would already be checked by the rook and hence it would be impossible for the king to stay in that position.
But it is assured that this position can be reached without any breach of rules. Does anyone know how this can be done?