n = io.read("*n")
a, b = {}, {}
for i = 1, n do a[i], b[i] = io.read("*n", "*n") end
t = {}
for i = 1, n do
  z = a[i] * 2000 + b[i]
  if t[z] then print("Yes") os.exit() end
  t[z] = true
end
print("No")