#include<iostream>
#include<vector>
#include<set>

using namespace std;

struct dnk
{
    int fir, sec, th, fou;
};

vector<dnk> a(int(1e5)), pref(int(1e5));
set<dnk> used;
dnk pr;

int main()
{
    int n, k;
    cin >> n >> k;

    for(int i  =0; i < n; i++)
    {
        char x;
        cin >> x;
        if (x == 'A') a[i].fir++;
        if(x == 'C') a[i].sec++;
        if (x == 'G') a[i].th++;
        if (x == 'T') a[i].fou++;

        if(i)
        {

            pref[i].fir = pref[i - 1].fir + a[i].fir;
            pref[i].sec = pref[i - 1].sec + a[i].sec;
            pref[i].th = pref[i - 1].th + a[i].th;
            pref[i].fou = pref[i - 1].fou + a[i].fou;
        }
        else
        {
            pref[i].fir = a[i].fir;
            pref[i].sec = a[i].sec;
            pref[i].th = a[i].th;
            pref[i].fou = a[i].fou;
        }
    }

    for(int i = k; i < n; i++)
    {
        pr.fir = pref[i].fir - pref[i - k].fir;
        pr.sec = pref[i].sec - pref[i - k].sec;
        pr.th = pref[i].th - pref[i - k].th;
        pr.fou = pref[i].fou - pref[i - k].fou;
        used.insert(pr);
    }

    cout << used.size();
}