/// Msaa el 5ra
#pragma GCC optimize("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("avx,avx2,fma")

#include "bits/stdc++.h"

using namespace std;

#define pb push_back
#define F first
#define S second
#define f(i, a, b)  for(int i = a; i < b; i++)
#define all(a)  a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define sz(x) (int)(x).size()
#define mp(x, y) make_pair(x,y)
#define popCnt(x) (__builtin_popcountll(x))
#define int ll

using ll = long long;
using ii = pair<int, int>;
using ull = unsigned long long;

const int N = 5e5 + 5, LG = 18, MOD = 1e9 + 7;
const long double PI = acos(-1);
const long double EPS = 1e-7;
int tr[N][26];
int sz[N], ptr;
int par[N];

void add(string s) {
    sz[0] += 1;
    int cur = 0;
    for (char c: s) {
        if (!tr[cur][c - 'a']) {
            tr[cur][c - 'a'] = ++ptr;
            par[ptr] = cur;
        }
        cur = tr[cur][c - 'a'];
        sz[cur] += 1;
    }
}

set<ii> st;

void killNode(int node) {
    st.erase({sz[node], node});
    f(k, 0, 26)
        if (tr[node][k])
            killNode(tr[node][k]);
}

void doWork() {
    int n, k;
    cin >> n >> k;
    f(i, 0, n) {
        string s;
        cin >> s;
        add(s);
    }
    for (int i = 0; i <= ptr; i++) {
        st.insert({sz[i], i});
    }
    int ans = 0;
    while (st.size() && st.rbegin()->F) {
        auto it = st.upper_bound({k + 1, -1});
        --it;
        int node = it->S;
        ans += 1;
        killNode(node);
        int cur = node;
        do {
            cur = par[cur];
            st.erase({sz[cur], cur});
            sz[cur] -= sz[node];
            st.insert({sz[cur], cur});
        } while (cur);
    }
    cout << ans << '\n';
}

int32_t main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif // ONLINE_JUDGE

    int t = 1;
//    cin >> t;
    while (t--) {
        doWork();
    }
}