#include <iostream>
using namespace std;
#define maxn 200005

int n,k;
char a[maxn];
int sol[30];
int counter[30];

int main()
{
    int i,k,size=0,rez=0;
    cin>>n>>k;
    cin>>a;
    if(k>1)
        for(i=0;i<n-1;++i){
            if(a[i]==a[i+1]){
                counter[a[i]%26]++;
                if(counter[a[i]%26]==(k-1))
                    ++sol[a[i]%26],counter[a[i]%26]=0,++i;
            }else
                counter[a[i]%26]=0;
        }
    else
        for(i=0;i<n;++i)
            ++sol[a[i]%26];

    if(k>1&&a[n-1]==a[n-2]&&(counter[a[n-1]%26]+1)==(k-1))
        ++sol[a[n-1]%26];

    for(i=0;i<28;++i)
        if(sol[i]>rez)
            rez=sol[i];
    cout<<rez;
}