Problem:
Score : 100 points

Problem Statement

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.

Sample Input 1

100 17

Sample Output 1

83

17 out of the initial 100 grams of sand will be consumed, resulting in 83 grams.

Sample Input 2

48 58

Sample Output 2

0

All 48 grams of sand will be gone, resulting in 0 grams.

Sample Input 3

1000000000 1000000000

Sample Output 3

0

Solution in Ruby (2.3.3) (judge verdict: Runtime Error)

n = gets.to_i
arr = gets.split(" ").map{|x|
	x.to_i
}

keys = []
arr.each do |x|
	keys << x-1
	keys << x
	keys << x+1
end
max = 0
keys.uniq.each do |x|
	cnt = keys.count(x)
	if max < cnt then
		max = cnt
	end
end
p max