#include <algorithm>
#include <array>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <optional>
#include <queue>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

int main() {
    int32_t n, k;
    cin >> n >> k;
    vector<vector<int32_t>> tr(n);
    for (auto i = 0; i < n - 1; ++i) {
        int32_t a, b;
        cin >> a >> b;
        --a;
        --b;
        tr[a].push_back(b);
        tr[b].push_back(a);
    }
    if (k > n) {
        cout << -1 << endl;
        return 0;
    }
    queue<pair<int32_t, int32_t>> que;
    que.push({0, 0});
    vector<bool> visited(n);
    visited[0] = true;
    --k;
    while (k > 0) {
        auto p = que.front();
        que.pop();
        for (auto v : tr[p.first]) {
            if (visited[v])
                continue;
            que.push({v, p.second + 1});
            visited[v] = true;
            --k;
        }
    }
    int64_t ans = 0;
    while (!que.empty()) {
        ans += que.front().second;
        que.pop();
    }
    cout << ans << endl;
    return 0;
}