local n = io.read("*n")
local h = {}
for i = 1, n do h[i] = io.read("*n") end
local tasks = {}
local tasknum, done = 0, 0
table.insert(tasks, 1 + n * 101)
tasknum = 1

local function getmin(l, r)
  local min, minpos = h[l], l
  for i = l + 1, r do
    if(h[i] < min) then
      min, minpos = h[i], i
    end
  end
  return min, minpos
end

local tot = 0
local curtask = 0
while(done < tasknum) do
  done = done + 1
  local task = tasks[done]
  local left, right = task % 101, task // 101
  local min, minpos = getmin(left, right)
  for i =left, right do
    h[i] = h[i] - min
  end
  if(left < minpos) then
    tasknum = tasknum + 1
    table.insert(tasks, left + (minpos - 1) * 101)
  end
  if(minpos < right) then
    tasknum = tasknum + 1
    table.insert(tasks, minpos + 1 + right * 101)
  end
  tot = tot + min
end
print(tot)
