#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N, K;
	cin >> N >> K;
	vector g(N, vector<int>());
	REP(i, N - 1) {
		int a, b;
		scanf("%d %d", &a, &b);
		--a; --b;
		g[a].emplace_back(b);
		g[b].emplace_back(a);
	}
	if (N < K) { puts("-1"); return 0; }
	vector<int> cnt(N);
	auto dfs = [&](auto self, int u, int d, int par) -> void {
		++cnt[d];
		for (int v : g[u]) {
			if (v == par) continue;
			self(self, v, d + 1, u);
		}
	};
	dfs(dfs, 0, 0, -1);
	ll ans = 0;
	for (int i = 0; i < N; ++i) {
		int cur = min(cnt[i], K);
		ans += (ll)cur * i;
		K -= cur;
	}
	cout << ans << endl;
}