gistfile1.txt

def give_greates_common_divisor(x,y)
  x.to_i.gcd(y.to_i)
end

puts "Give the first number"
x = gets
puts "Give the second number"
y = gets


puts "the greates common divisor is: " + 

give_greates_common_divisor(x,y).to_s


-.------------------

Result in console :

Give the first number
10
Give the second number
20
the greates common divisor is: 10