Categorize the following sentences into declarative, interrogative, exclamative, and imperative.
Let us fly
The sentence "Let us fly" is an imperative sentence.
Complete the following task based on the instruction and optional input provided.### Instruction:
Categorize the following sentences into declarative, interrogative, exclamative, and imperative.

### Input:
Let us fly

### Output:
The sentence "Let us fly" is an imperative sentence.