The given pattern consists of three rows. In the first row, the letters D, I, and M are written. In the second row, the letters P, A, and P are written. In the third row, the letters P, U, and O are written. The pattern suggests that the letters in the second row are the same as the first row, but shifted one position to the right in the alphabet. Similarly, the letters in the third row are the same as the second row, but shifted one position to the right in the alphabet. Therefore, the missing letter in the third row should be one position to the right of O, which is P.