#include <bits/stdc++.h>
using namespace std;

using vi = vector<int>; using vvi = vector<vi>; using vvvi = vector<vvi>;
using ll = long long int;
using vll = vector<ll>; using vvll = vector<vll>; using vvvll = vector<vvll>;
using vd = vector<double>; using vvd = vector<vd>; using vvvd = vector<vvd>;
using P = pair<int, int>;
using Pll = pair<ll, ll>;
using cdouble = complex<double>;

const double eps = 1e-9;
const double INFD = numeric_limits<double>::infinity();
const double PI = 3.14159265358979323846;
#define Loop(i, n) for(int i = 0; i < (int)(n); i++)
#define Loop1(i, n) for(int i = 1; i <= (int)(n); i++)
#define Loopr(i, n) for(int i = (int)(n) - 1; i >= 0; i--)
#define Loopr1(i, n) for(int i = (int)(n); i >= 1; i--)
#define Foreach(buf, container) for(auto buf : container)
#define Loopdiag(i, j, h, w, sum) for(int i = ((sum) >= (h) ? (h) - 1 : (sum)), j = (sum) - i; i >= 0 && j < (w); i--, j++)
#define Loopdiagr(i, j, h, w, sum) for(int j = ((sum) >= (w) ? (w) - 1 : (sum)), i = (sum) - j; j >= 0 && i < (h); j--, i++)
#define Loopdiagsym(i, j, h, w, gap) for (int i = ((gap) >= 0 ? (gap) : 0), j = i - (gap); i < (h) && j < (w); i++, j++)
#define Loopdiagsymr(i, j, h, w, gap) for (int i = ((gap) > (h) - (w) - 1 ? (h) - 1 : (w) - 1 + (gap)), j = i - (gap); i >= 0 && j >= 0; i--, j--)
#define Loopitr(itr, container) for(auto itr = container.begin(); itr != container.end(); itr++)
#define printv(vector) Loop(ex_i, vector.size()) { cout << vector[ex_i] << " "; } cout << endl;
#define printmx(matrix) Loop(ex_i, matrix.size()) { Loop(ex_j, matrix[ex_i].size()) { cout << matrix[ex_i][ex_j] << " "; } cout << endl; }
#define quickio() ios::sync_with_stdio(false); cin.tie(0);
#define bitmanip(m,val) static_cast<bitset<(int)m>>(val)
#define Comp(type_t) bool operator<(const type_t &another) const
#define fst first
#define snd second
bool nearlyeq(double x, double y) { return abs(x - y) < eps; }
bool inrange(int x, int t) { return x >= 0 && x < t; }
bool inrange(vi xs, int t) { Foreach(x, xs) if (!(x >= 0 && x < t)) return false; return true; }
ll rndf(double x) { return (ll)(x + (x >= 0 ? 0.5 : -0.5)); }
ll floorsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (m * m <= x ? 0 : -1); }
ll ceilsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (x <= m * m ? 0 : 1); }
ll rnddiv(ll a, ll b) { return (a / b + (a % b * 2 >= b ? 1 : 0)); }
ll ceildiv(ll a, ll b) { return (a / b + (a % b == 0 ? 0 : 1)); }
ll gcd(ll m, ll n) { if (n == 0) return m; else return gcd(n, m % n); }
ll lcm(ll m, ll n) { return m * n / gcd(m, n); }

/*******************************************************/

// range = [l, r), return last value causing "t" in evalfunc that returns l->[t,...,t,f,...,f)->r
// NOTE: if [f,...,f) then return l - 1, if [l, r) = empty set then invalid use
template<typename val_t, typename bsargv_t>
val_t lower_binary_search(val_t l, val_t r, const bsargv_t &v, bool(*evalfunc)(val_t, const bsargv_t&)) {
	if (r - l == 1) {
		if (evalfunc(l, v)) return l;
		else return l - 1;
	}
	val_t m = (l + r) / 2;
	if (evalfunc(m, v)) return lower_binary_search<val_t, bsargv_t>(m, r, v, evalfunc);
	else return lower_binary_search<val_t, bsargv_t>(l, m, v, evalfunc);
}

struct bsargv_t {
	vi cnt;
	int k;
};

bool evalfunc(int val, const bsargv_t &v) {
	priority_queue<int, vi, greater<int>> pq;
	Loop(i, val) pq.push(0);
	vi buf;
	Loop(i, 26) {
		Loop(j, min(val, v.cnt[i])) {
			int x = pq.top(); pq.pop();
			buf.push_back(x + 1);
		}
		while (buf.size()) {
			pq.push(buf.back());
			buf.pop_back();
		}
	}
	if (pq.size() && pq.top() >= v.k) return true;
	else return false;
}

int main() {
	int n, k; cin >> n >> k;
	vi cnt(26);
	Loop(i, n) {
		string s; cin >> s;
		cnt[s[0] - 'A']++;
	}
	bsargv_t v = { cnt, k };
	cout << lower_binary_search<int>(1, n + 1, v, evalfunc) << endl;
}

Measured memory_bytes: 428