local n, m = io.read("*n", "*n")
local color = {}
local edge = {}
for i = 1, n do
  color[i] = 0
  edge[i] = {}
end
local tasks = {}
do
  local a, b = io.read("*n", "*n")
  color[a] = 1
  color[b] = 2
  tasks[1] = a
  tasks[2] = b
  table.insert(edge[a], b)
  table.insert(edge[b], a)
end
for i = 2, m do
  local a, b = io.read("*n", "*n")
  table.insert(edge[a], b)
  table.insert(edge[b], a)
end
local allsame = false
for itask = 1, n do
  local src = tasks[itask]
  for j = 1, #edge[src] do
    local dst = edge[src][j]
    if color[dst] == 0 then
      color[dst] = 3 - color[src]
      table.insert(tasks, dst)
    elseif color[dst] == color[src] then
      allsame = true
      break
    end
  end
  if allsame then break end
end
if allsame then
  print(n * (n - 1) // 2 - m)
else
  local cnt1, cnt2 = 0, 0
  for i = 1, n do
    if color[i] == 1 then
      cnt1 = cnt1 + 1
    else
      cnt2 = cnt2 + 1
    end
  end
  print(cnt1 * cnt2 - m)
end
