; Enter your code here. Read input from STDIN. Print output to STDOUT
;
(require '[clojure.string :as str])

(defn dis [a b]
    (Math/sqrt (+ (Math/pow (- (first b) (first a)) 2) (Math/pow (- (second b) (second a)) 2)))
)

(defn split-to-double [input]
    (->> (str/split input #"\s")
        (map #(Double/parseDouble %))
        (into [])
    )
)

(defn get-points-vector [number-of-points]
    (->> #(split-to-double (read-line))
        (repeatedly number-of-points)
        (into [])
    )
)


(let [points (Integer/parseInt (read-line))
    points_vector (get-points-vector points)
    ]
    (loop [x points_vector r 0]
        (if (empty? (rest x))
            (do
                (println (+ r (dis (first x) (first points_vector) )))
            )
            (recur (rest x) (+ r (dis (first x) (second x))))
        )
    )
)