#include <bits/stdc++.h>
const int maxN = 1e6 + 1;
using namespace std;

int sap[maxN], ngua[maxN];

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

    s = " " + s;

    fill(ngua, ngua + maxN, 0);
    fill(sap, sap + maxN, 0);
    if(s[1] == 'O') ngua[1] = 1;
    else sap[1] = 1;
    for(int i = 1; i <= n; ++i)
    {
        if(s[i] == 'O')
            ngua[i] = ngua[i - 1] + 1;
        else
            ngua[i] = ngua[i - 1];
        if(s[i] == 'R')
            sap[i] = sap[i - 1] + 1;
        else
            sap[i] = sap[i - 1];
    }

    int ans;

    int tmp = n/(k+1) * (k+1);

    for(int kc = tmp; kc >= 1; kc -= (k+1))
    {
        for(int i = 1; i <= n - kc + 1; ++i)
        {
            if((ngua[i+kc-1] - ngua[i-1]) == k * (sap[i+kc-1] - sap[i-1]))
            {
                ans = kc;
                goto xyz;
            }
        }
    }

xyz:   cout << ans << endl;
}