def extgcd(a,b)
  return [1,0] if b == 0
  y,x = extgcd(b, a % b)
  y -= (a/b)*x
  return [x,y]
end

def mod_inverse(a, mod)
  x,y = extgcd(a, mod)
  return x % mod
end

def chinese_remainder(m1,m2,a,b)
  u1, u2 = extgcd(m1, m2)
  return nil if (a - b) % m1.gcd(m2) != 0
  l = (a - b) / (m1.gcd(m2))
  return (a - m1 * u1 * l) % (m1 * m2 / m1.gcd(m2))
end

n = gets.to_i
x = Array.new(n)
y = Array.new(n)
n.times do |i|
  x[i], y[i] = gets.split.map(&:to_i)
end
ans, mod = 0, 1
x.zip(y).each do |x,y|
  ans = chinese_remainder(mod, y, ans, x)
  unless ans
    puts -1
    exit
  end
  mod = mod * y / mod.gcd(y)
end
ans += mod if ans == 0
puts ans % 1000000007