Calculate the age difference between the given two people.
Person 1: 40 years old
Person 2: 20 years old
The age difference between Person 1 and Person 2 is 20 years.
Complete the following task based on the instruction and optional input provided.### Instruction:
Calculate the age difference between the given two people.

### Input:
Person 1: 40 years old
Person 2: 20 years old

### Output:
The age difference between Person 1 and Person 2 is 20 years.