Problem Description

Given the snow depth $ H_1 $ at a certain time and the snow depth $ H_2 $ one hour before, calculate and output the difference in snow depth $ H_1 - H_2 $ over this hour.

Input Format

The input is provided from standard input in the following format:

$ H_1 $ $ H_2 $

1. The first line contains an integer representing the snow depth at a certain time $H_1\ (0\leq H_1 \leq 2,000)$.
2. The second line contains an integer representing the snow depth one hour before $H_2\ (0\leq H_2 \leq 2,000)$.

Output Format

Output the difference in snow depth $ H_1 - H_2 $ in one line.
Ensure a newline character is included at the end of the output.

Sample Input and Output

Sample Input #1

15
10

Sample Output #1

5

Sample Input #2

0
0

Sample Output #2

0

Sample Input #3

5
20

Sample Output #3

-15

Notes/Hints

None

见题面 Input 部分

见题面 Output 部分