'''

@author: olivier.massot, 2019
'''
import math

def distance(c0, c1):
    return math.sqrt((c0[0] - c1[0])**2 + (c0[1] - c1[1])**2)

cities = [tuple([int(j) for j in input().split()]) for _ in range(int(input()))]

dist, start = 0, cities.pop(0)

current = start
while cities:
    cities.sort(key=lambda c: distance(c, current))
    next_step = cities.pop(0)
    dist += distance(next_step, current)
    current = next_step

dist += distance(next_step, start)
print(round(dist))