#include <bits/stdc++.h>
using namespace std;
#define ll long long
signed main() {
    int n, k; cin >> n >> k;
    int tot = 1;
    int root = 1;
    vector<array<int, 26>> ch(3e5 + 10, array<int, 26>{});
    vector<int> ed(3e5 + 10), siz(3e5 + 10);
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        string s; cin >> s;
        int m = s.size();
        s = ' ' + s;
        int now = root;
        for (int j = 1; j <= m; j++) {
            if (ch[now][s[j] - 'a'] == 0) {
                ch[now][s[j] - 'a'] = ++tot;
            }
            now = ch[now][s[j] - 'a'];
        }
        ed[now]++;
    }
    function<void(int)> dfs = [&] (int x) {
        // cout << "x : " << x << '\n';
        siz[x] = ed[x];
        vector<int> t;
        for (int i = 0; i <= 25; i++) {
            if (ch[x][i]) {
                dfs(ch[x][i]);
                siz[x] += siz[ch[x][i]];
                t.push_back(siz[ch[x][i]]);
            }
        }
        sort(t.begin(), t.end());
        reverse(t.begin(), t.end());
        if (siz[x] > k) {
            // cout << "? : " << '\n';
            for (int j = 0; j < (int)t.size(); j++) {
                if (siz[x] > k) {
                    ans++;
                    siz[x] -= t[j];
                }
                else {
                    break;
                }
            }
        }
    };
    dfs(root);
    cout << ans + 1 << '\n';
    return 0;
}
/*
4 2
a
abc
abd
b
*/