The prosecution did not waive its right to raise the waiver defense here where the government filed a motion to dismiss the appeal before filing appellee’s brief. Moreover, the court could dismiss the appeal even if the prosecution could not raise the issue. When appellant waived, in writing, his right to appeal any sentence imposed by the court as a condition of his plea agreement, under the parol evidence rule, the court will not look to extrinsic evidence to interpret an unambiguous written instrument. Moreover, because appellant failed to raise the issue of whether the appeal waiver was knowing and intelligent when he filed his appellant’s opening brief, that issue is waived. Finally, when appellant waived his statutory right to appeal his sentence, he effectively waived his right to argue ineffective assistance of counsel involving the sentencing issue on direct appeal.