local ior = io.input()
local n, m = ior:read("*n", "*n")
local t = {}
local parent = {}
for i = 1, n do t[i], parent[i] = 0, i end

local function findroot(idx)
  while(parent[idx] ~= idx) do
    idx = parent[idx]
  end
  return idx
end

for i = 1, m do
  local a, b = ior:read("*n", "*n")
  a, b = a + 1, b + 1
  -- !! [ some inputs contain S_a = S_b ] !!
  if(a ~= b) then
    t[a], t[b] = t[a] + 1, t[b] + 1
  end
  local ra, rb = findroot(a), findroot(b)
  parent[a], parent[b], parent[rb] = ra, ra, ra
end
local oddnum = 0
for i = 1, n do
  if(t[i] % 2 == 1) then oddnum = oddnum + 1 end
end

local groupnum = 0
local grouplist = {}
for i = 1, n do
  local r = findroot(i)
  if(r ~= i) then grouplist[r] = true end
end
for k, v in pairs(grouplist) do
  groupnum = groupnum + 1
end
if(oddnum ~= 2 and oddnum ~= 0) then print("NO")
elseif(2 <= groupnum) then print("NO")
else print("YES")
end