import sys
from collections import deque

def main():
    sys.setrecursionlimit(1 << 25)
    input = sys.stdin.read().split()
    idx = 0
    N, K = int(input[idx]), int(input[idx+1])
    idx +=2
    edges = [[] for _ in range(N+1)]
    for _ in range(N-1):
        a = int(input[idx])
        b = int(input[idx+1])
        edges[a].append(b)
        edges[b].append(a)
        idx +=2
    
    if K > N:
        print(-1)
        return
    
    depth = [0]*(N+1)
    visited = [False]*(N+1)
    q = deque()
    q.append(1)
    visited[1] = True
    order = []
    while q:
        u = q.popleft()
        order.append(u)
        for v in edges[u]:
            if not visited[v]:
                visited[v] = True
                depth[v] = depth[u] +1
                q.append(v)
    
    selected = [False]*(N+1)
    for i in range(K):
        selected[order[i]] = True
    
    children = [[] for _ in range(N+1)]
    parent = [0]*(N+1)
    visited = [False]*(N+1)
    q = [1]
    visited[1] = True
    while q:
        u = q.pop()
        for v in edges[u]:
            if not visited[v]:
                visited[v] = True
                parent[v] = u
                children[u].append(v)
                q.append(v)
    
    has_selected = [False]*(N+1)
    
    def dfs(u):
        if selected[u]:
            has_selected[u] = True
        for v in children[u]:
            dfs(v)
            if has_selected[v]:
                has_selected[u] = True
    
    dfs(1)
    
    ans =0
    for u in range(1, N+1):
        for v in children[u]:
            if has_selected[v]:
                ans +=1
    print(ans)

if __name__ == "__main__":
    main()