from collections import deque

n, k = map(int, input().split())
if n < k:
    print(-1)
    exit()

edges = [[] for _ in range(n)]
for _ in range(n - 1):
    a, b = map(int, input().split())
    edges[a - 1].append(b - 1)
    edges[b - 1].append(a - 1)

queue = deque()
queue.append(0)
queue.append(0)
ans = 0
check = [False for _ in range(n)]
check[0] = True
while queue:
    if k == 0:
        break
    pos = queue.popleft()
    cnt = queue.popleft()
    ans += cnt
    k -= 1
    for n_pos in edges[pos]:
        if check[n_pos]:
            continue
        check[n_pos] = True
        queue.append(n_pos)
        queue.append(cnt + 1)
print(ans)