local ior = io.input()
local n, m = ior:read("*n", "*n")
local t = {}
for i = 1, n do t[i] = 0 end
for i = 1, m do
  local a, b = ior:read("*n", "*n")
  a, b = a + 1, b + 1
  t[a], t[b] = t[a] + 1, t[b] + 1
end
local oddnum = 0
for i = 1, n do
  if(t[i] % 2 == 1) then oddnum = oddnum + 1 end
end
print((oddnum == 2 or oddnum == 0) and "YES" or "NO")