import heapq
def prim_heap():
    used = [True] * n #True:不使用
    edgelist = []
    for e in edge[0]:
        heapq.heappush(edgelist,e)
    used[0] = False
    res = 0
    counter = 1
    while counter != n:
        minedge = heapq.heappop(edgelist)
        if not used[minedge[1]]:
            continue
        v = minedge[1]
        used[v] = False
        for e in edge[v]:
            if used[e[1]]:
                heapq.heappush(edgelist,e)
        res += minedge[0]
        counter += 1
    return res

#########################
n = int(input())

#隣接リストの作成 edge[i]:[コスト,行先]
edge = [[] for i in range(n)]
x_sort = [] #[Xi,Yi,点番号]
y_sort = [] #[Yi,Xi,点番号]
for i in range(n):
    X,Y = map(int,input().split())
    x_sort.append([X,Y,i])
    y_sort.append([Y,X,i])
x_sort.sort()
y_sort.sort()
for i in range(1,n):
    edge[x_sort[i][2]].append([min(abs(x_sort[i][0]-x_sort[i-1][0]),abs(x_sort[i][1]-x_sort[i-1][1])),x_sort[i-1][2]])
    edge[x_sort[i-1][2]].append([min(abs(x_sort[i][0]-x_sort[i-1][0]),abs(x_sort[i][1]-x_sort[i-1][1])),x_sort[i][2]])
    edge[y_sort[i][2]].append([min(abs(y_sort[i][0]-y_sort[i-1][0]),abs(y_sort[i][1]-y_sort[i-1][1])),y_sort[i-1][2]])
    edge[y_sort[i][2]].append([min(abs(y_sort[i][0]-y_sort[i-1][0]),abs(y_sort[i][1]-y_sort[i-1][1])),y_sort[i-1][2]])
print(prim_heap())