Rewrite the following sentence to make it more concise:

He was not able to understand the intricate details of the problem, so he decided to call for assistance.
He couldn't grasp the problem's complexity, so he sought help.
Complete the following task based on the instruction and optional input provided.### Instruction:
Rewrite the following sentence to make it more concise:

He was not able to understand the intricate details of the problem, so he decided to call for assistance.

### Output:
He couldn't grasp the problem's complexity, so he sought help.