We have a sandglass that runs for X seconds. The sand drops from the upper bulb at a rate of 1 gram per second. That is, the upper bulb initially contains X grams of sand.

How many grams of sand will the upper bulb contains after t seconds?

Constraints

• 1≤X≤10^9
• 1≤t≤10^9
• X and t are integers.

Input

The input is given from Standard Input in the following format:

X t

Output

Print the number of sand in the upper bulb after t second.

Examples

Input

100 17

Output

83

Input

48 58

Output

0

Input

1000000000 1000000000

Output

0

见题面

见题面