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.strip.to_i
a = gets.strip.split(' ').map(&:to_i)
l = 0
m = 0
n = 0
numbe = []
x = []
num = 1

a.each do |c|
  x = a.select{ |n| (c-1-n).abs <= 1}
  l = x.size
  x = a.select{ |n| (c-n).abs <= 1}
  m = x.size
  x = a.select{ |n| (c+1-n).abs <= 1}
  n = x.size
  numbe[num-1] = l
  numbe[num] = m
  numbe[num+1] = n
  num = num + 3
end
p numbe.max