input: Write a python function to find the closest sum of three numbers in an array to a given number.
  assert find_closest_sum([1, 2, 3, 4, 5], 10) == 9
  assert find_closest_sum([-1, 2, 1, -4], 1) == 2
  assert find_closest_sum([0, 0, 0], 1) == 0
  assert find_closest_sum([1, 1, 1, 0], 100) == 3
output: def find_closest_sum(nums, target):
      nums.sort()
      closest_sum = float('inf')
      
      for i in range(len(nums) - 2):
          left, right = i + 1, len(nums) - 1
          
          while left < right:
              current_sum = nums[i] + nums[left] + nums[right]
              
              if abs(current_sum - target) < abs(closest_sum - target):
                  closest_sum = current_sum
              
              if current_sum < target:
                  left += 1
              elif current_sum > target:
                  right -= 1
              else:
                  return current_sum
      
      return closest_sum