n = gets.to_s.to_i
y = gets.to_s.split.map{|t| t.to_i }

inf = 10**4 * n
dp = [inf] * (y.max + 1)
dp[0] = 0

m = 0
y.each_with_index do |t, i|
  
  m = t if m < t
  
  dp[0] = dp[0] + t
  
  1.upto(t) do |j|
    dp[j] = [dp[j] + t - j, dp[j-1] - 1 ].min
  end
  
  (t+1).upto(m) do |j|
    dp[j] = [dp[j] + j - t, dp[j-1] + 1 ].min
  end
end

ans = dp.min
puts ans