local n, m = io.read("*n", "*n")
local t = {}
for i = 1, n do t[i] = true end
for i = 1, m do
  local a, b = io.read("*n", "*n")
  t[a] = not t[a]
  t[b] = not t[b]
end
local ret = true
for i = 1, n do ret = ret and t[i] end
print(ret and "YES" or "NO")
