Problem:
Greatest Common Divisor

Write a program which finds the greatest common divisor of two natural numbers a and b

Input

a and b are given in a line sparated by a single space.

Output

Output the greatest common divisor of a and b.

Constrants

1 ≤ a, b ≤ 109

Hint

You can use the following observation:

For integers x and y, if x ≥ y, then gcd(x, y) = gcd(y, x%y)

Sample Input 1

54 20

Sample Output 1

2

Sample Input 2

147 105

Sample Output 2

21

Solution in Ruby (judge verdict: Time Limit Exceeded)

def gcd(x,y)
 min = x<=y ? x : y
 result = 1
 unless x<=y
  min.times{|i|
   result=i+1 if x%(i+1)==0 && y%(i+1)==0
  }
 else
  min.times{|i|
   result=i+1 if y%(i+1)==0 && (x%y)%(i+1)==0
  }
 end
 result
 
end
x,y=gets.split.map{|num|num.to_i}
puts gcd x,y