from heapq import *
n=int(input())
neighbors = {}

for x in range(n):
    neighbors[x] = []
for i in range(n-1):
    a, b = map(int,input().split())
    neighbors[a-1].append(b-1)
    neighbors[b-1].append(a-1)
def search(source):
    ans = 0
    cur_max = 0
    cur_len = 0
    heap = [source]
    vis = [False for i in range(n)]
    while len(heap) > 0:
        x = heappop(heap)
        cur_max = max(cur_max, x)
        cur_len += 1
        vis[x] = True
        if cur_max - source + 1 == cur_len:
            ans += 1
        for y in neighbors[x]:
            if y >= source and vis[y] == False:
                heappush(heap, y)
    return ans
ans = 0
prev = 0
for x in range(n-1, -1, -1):
    neigh = 0
    plus = 0
    for y in neighbors[x]:
        if y > x:
            neigh += 1
        if y == x + 1:
            plus = 1
    if plus == neigh and plus == 1:
        prev += 1
    else:
        prev = search(x)
    ans += prev
print(ans)