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

inf = 10**4 * n
m = y.max
dp = Array.new(n+1){ [inf] * (m+1) }
dp[0][0] = 0

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