local mmi, mma = math.min, math.max
local n = io.read("*n")
local odd, even = -1000000007 * 200010, 0
for i = 1, n do
  local a = io.read("*n")
  odd, even = mma(odd, even - a), mma(even, odd + a)
end
local ans = mma(odd, even)
ans = tostring(1LL * ans):gsub("LL", "")
print(ans)