input: Write a python function to find the length of the longest increasing subsequence in a list of numbers.
  assert longest_increasing_subsequence([1, 10, 3, 11, 7, 8, 4, 2]) == 3
  assert longest_increasing_subsequence([5, 6, 7, 8, 9]) == 5
  assert longest_increasing_subsequence([9, 8, 7, 6, 5]) == 1
output: def longest_increasing_subsequence(nums):
      if not nums:
          return 0
          
      dp = [1] * len(nums)
  
      for i in range(1, len(nums)):
          for j in range(i):
              if nums[i] > nums[j]:
                  dp[i] = max(dp[i], dp[j] + 1)
      
      return max(dp)