local mmi, mma = math.min, math.max
local n = io.read("*n")
local a = {}
for i = 1, n do
  a[i] = io.read("*n")
end
local odd, even = -a[1], -1000000007 * 200010
for i = 2, n do
  local ai = a[i]
  odd, even = mma(odd, even - ai, -ai), mma(even, odd + ai)
end
local ans = mma(odd, even)
ans = tostring(1LL * ans):gsub("LL", "")
print(ans)