/*
┓┏┓┏┓┃
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┓┏┓┏┓┃
┛┗┛┗┛┃
┓┏┓┏┓┃＼○／
┛┗┛┗┛┃ / /
┓┏┓┏┓┃ノ
┛┗┛┗┛┃
┓┏┓┏┓┃
┛┗┛┗┛┃
┓┏┓┏┓┃
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      MIPTCLASSICMIPTCLASSICMIPTCLASSICMIPTCLASSICMIPTCLASSICMIPTCLASSIC
*/

// #define pragma

#ifdef pragma
#pragma GCC optimize("Ofast")
#pragma GCC optimize("no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
#pragma GCC diagnostic ignored "-Wunused-result"
#endif // pragma

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ll long long
#define all(x) begin(x), end(x)
#define pb push_back
#define x first
#define y second
#define int long long
#define zero(two) memset(two, 0, sizeof(two))

using namespace std;
using namespace __gnu_pbds;


typedef vector<int> vi;
typedef vector<bool> vb;
typedef pair<int, int> pii;
typedef long double ld;
typedef vector<vi> matrix;
template<typename T>
using kawaii_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = atan2(0, -1);

void seriy() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(10);
    #if 0
        freopen("input", "r", stdin);
        freopen("output", "w", stdout);
    #endif
}

const int INF = 1e18 + 7;

signed main() {
    seriy();
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    int ans = 0;
    for(int i = 'a'; i <= 'z'; i++) {
        vi cc;
        for(int j = 0; j < n; j++) {
            int x = j;
            int cnt = 0;
            while(x < n && s[x] == s[j]) {
                cnt++;
                x++;
            }
            if(s[j] == i) cc.pb(cnt);
            j = x - 1;
        }
        int ans1 = 0;
        for(auto i : cc) {
            ans1 += i / k;
        }
        ans = max(ans, ans1);
    }
    cout << ans;
    return 0;
}