local n = io.read("*n")
local a = {}
local b = {}
for i = 1, n do
  a[i] = io.read("*n")
  b[i] = io.read("*n")
end
local left, right = {a[1] - b[1]}, {b[n] - a[n]}
for i = 2, n do
  left[i] = left[i - 1] + a[i] - b[i]
  right[i] = right[i - 1] + b[n + 1 - i] - a[n + 1 - i]
end
local mma = math.max
local ret = mma(left[n], right[n])
for i = 1, n - 1 do
  ret = mma(ret, left[i] + right[n - i])
end
print(ret)