#!/usr/bin/env ruby

def parse_tree(input, start)
  num_children = input[start]
  num_metadata = input[start + 1]

  children = []
  next_index = start + 2
  while num_children > 0 do
    sum, endindex = parse_tree(input, next_index)
    children << sum
    next_index = endindex + 1
    num_children -= 1
  end

  value = 0
  if children.empty?
    while num_metadata > 0 do
      value += input[next_index]
      next_index += 1
      num_metadata -= 1
    end
  else
    while num_metadata > 0 do
      i = input[next_index]
      value += children[i - 1] if i <= children.length
      next_index += 1
      num_metadata -= 1
    end
  end
  return [ value, next_index - 1 ]
end

input = gets.chomp.split.map(&:to_i)

puts parse_tree(input, 0)[0]