import collections, sys

sys.setrecursionlimit(1000000)

n, k = map(int, input().split())

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

if n < k:
    print(-1)
    exit(0)

childs = {}
def f(parent, current):
    if current in childs:
        return childs[current]
    
    v = 1
    for nxt in nxts[current]:
        if nxt != parent:
            v += f(current, nxt)
    childs[current] = v
    return v
f(-1, 0)

def g(parent, current, coin):
    if coin <= len(nxts[current]):
        return 1

    ans = 1
    for nxt in sorted(filter(lambda nxt: nxt != parent, nxts[current]), key=lambda child: len(nxts[child]), reverse=True):
        if coin <= childs[nxt]:
            ans += g(current, nxt, coin)
            break
        ans += g(current, nxt, childs[nxt])
        coin -= childs[nxt]
    return ans

print(g(-1, 0, k))