#include <algorithm>//min/max/sort(rand-access it)/merge
#include <array>
#include <bitset>
#include <climits>//INT_MAX/INT_MIN/ULLONG_MAX
#include <cmath>//fmin/fmax/fabs/sin(h)/cos(h)/tan(h)/exp/log/pow/sqrt/cbrt/ceil/floor/round/trunc
#include <cstdlib>//abs/atof/atoi/atol/atoll/strtod/strtof/..., srand/rand, calloc/malloc, exit, qsort
#include <iomanip>//setfill/setw
#include <iostream>//cin/cout/wcin/wcout/left/right/internal/dec/hex/oct/fixed/scientific
#include <iterator>
#include <list>
#include <queue>
#include <string>//stoi/stol/stoul/stoll/stoull/stof/stod/stold/to_string/getline
#include <tuple>
#include <utility>//pair
#include <valarray>
#include <vector>

#define PRIME_SHORT 10007
#define PRIME 1000000007

using namespace std;

typedef unsigned int ui;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, int> plli;
typedef pair<ull, int> puli;
typedef pair<double, int> pdi;
typedef pair<ll, ll> pllll;
typedef pair<ull, ull> pulul;
typedef pair<double, double> pdd;
typedef tuple<int, int, int> ti3;
typedef tuple<int, int, int, int> ti4;

const bool debug = false;

void rar(int n, string* a);
void rar2(int n, int m, int** a);

int ipow(int base, int exp);
int left(int current, bool swap);
int right(int current, bool swap);
int griddist(int x, int y, int s, int t);
int griddist(pii one, pii two);
double sqeucldist(double x, double y, double s, double t);
double sqeucldist(pii one, pii two);
ull modadd(ull a, ull b, int mod);
ull modmult(ull a, ull b, int mod);

int main(void) {
    ui n;
    cin >> n;
    size_t k;
    cin >> k;

    ui header_count[26];
    for (size_t i = 0; i < 26; ++i)
        header_count[i] = 0U;

    string p;
    for (size_t i = 0; i < n; ++i)
    {
        cin >> p;
        int index = p[0] - 'A';
        if (debug)
            cout << p << " " << index << endl;
        ++(header_count[index]);
    }

    list<ui> remaining;

    for (size_t i = 0; i < 26; ++i)
    {
        if (header_count[i] > 0)
            remaining.push_back(header_count[i]);
    }
    
    if (debug){
        cout << "remaining" << endl;
        for (list<ui>::iterator it = remaining.begin(); it != remaining.end(); ++it)
            cout << *it << "\t";
        cout << endl;
    }

    remaining.sort(greater<ui>());
    
    if (debug) {
        cout << "remaining" << endl;
        for (list<ui>::iterator it = remaining.begin(); it != remaining.end(); ++it)
            cout << *it << "\t";
        cout << endl;
    }

    ull count = 0UL;

    size_t s = remaining.size();
    while(s >= k) {
        if (debug) {
            for (list<ui>::iterator it = remaining.begin(); it != remaining.end(); ++it)
                cout << *it << " ";
            cout << endl;
        }

        int i = 0;
        for (list<ui>::iterator it = remaining.begin(); i < k; ++i)
        {
            --(*it);
            if (*it == 0) {
                it = remaining.erase(it);
                continue;
            }
            ++it;
        }
        ++count;
        remaining.sort(greater<ui>());
        s = remaining.size();
    }

    cout << count << endl;
    return 0;
}

void rar(int n, string* a)
{
    for (int i = 0; i < n; ++i)
    {
        cin >> a[i];
    }
    return;
}

void rar2(int n, int m, int** a)
{
    for (int i = 0; i < n; ++i)
    {
        a[i] = new int[m];
        for (int j = 0; j < m; ++j)
        {
            cin >> a[i][j];
        }
    }
    return;
}



















int ipow(int base, int exp) {
    int result = 1;
    while (exp)
    {
        if (exp & 1)
            result *= base;
        exp >>= 1;
        base *= base;
    }

    return result;
}
int left(int current, bool swap = false) {
    if(swap){
        return right(current, false);
    } else {
        return 2*current + 1;
    }
}
int right(int current, bool swap = false) {
    if(swap){
        return left(current, false);
    } else {
        return 2*(current+1);
    }
}
int griddist(int x, int y, int s, int t) {
    return abs(x-s) + abs(y-t);
}
int griddist(pii one, pii two) {
    return abs(one.first - two.first) + abs(one.second - two.second);
}
double sqeucldist(double x, double y, double s, double t) {
    double a = x-s;
    double b = y-t;
    return a*a+b*b;
}
double sqeucldist(pii one, pii two) {
    double a = one.first - two.first;
    double b = one.second - two.second;
    return a*a+b*b;
}

ull modadd(ull a, ull b, int mod) {
    return (a%mod + b%mod)%mod;
}
ull modmult(ull a, ull b, int mod) {
    return ((a%mod)*(b%mod))%mod;
}


Measured memory_bytes: 256