#include <bits/stdc++.h>

#include <bits/extc++.h>

using namespace std;

#define limit (100000 + 5)//防止溢出

#define INF 0x3f3f3f3f

#define inf 0x3f3f3f3f3f

#define lowbit(i) i&(-i)//一步两步

#define EPS 1e-6

#define FASTIO  ios::sync_with_stdio(false);cin.tie(0);

#define ff(a) printf("%d\n",a );

#define pi(a,b) pair<a,b>

#define rep(i, a, b) for(ll i = a; i <= b ; ++i)

#define per(i, a, b) for(ll i = b ; i >= a  ; --i)

#define MOD 998244353

#define traverse(u) for(int i = head[u]; ~i ; i = edge[i].next)

#define FOPEN freopen("C:\\Users\\tiany\\CLionProjects\\acm_01\\data.txt", "rt", stdin)

#define FOUT freopen("C:\\Users\\tiany\\CLionProjects\\acm_01\\dabiao.txt", "wt", stdout)

#define debug(x) cout<<x<<endl

typedef long long ll;

typedef unsigned long long ull;

inline ll read(){

    ll sign = 1, x = 0;char s = getchar();

    while(s > '9' || s < '0' ){if(s == '-')sign = -1;s = getchar();}

    while(s >= '0' && s <= '9'){x = (x << 3) + (x << 1) + s - '0';s = getchar();}

    return x * sign;

}//快读

void write(ll x){

    if(x < 0) putchar('-'),x = -x;

    if(x / 10) write(x / 10);

    putchar(x % 10 + '0');

}

int kase;

int n,k;

int dp[limit][3][22];

int c[limit];

int dfs(int cur, int gest, int tot){

    if(dp[cur][gest][tot])return dp[cur][gest][tot];

    if(cur > n)return 0;

    int ans = dfs(cur + 1, gest, tot);

    if(c[cur] == gest)++ans;

    if(tot > 0){

        int t,p;

        if(gest == 0)t = 1, p = 2;

        else if(gest == 2)t = 0,p = 1;

        else t = 0, p = 2;

        ans = max({ans, dfs(cur + 1, t, tot - 1), dfs(cur + 1, p, tot - 1)});

    }

    return dp[cur][gest][tot] = ans;

}

int main() {

#ifdef LOCAL

    FOPEN;

#endif

    FASTIO

    cin>>n>>k;

    rep(i,1,n){

        char cc;

        cin>>cc;

        if(cc == 'H'){

            c[i] = 0;

        }else if(cc == 'S'){

            c[i] = 1;

        }else{

            c[i] = 2;

        }

    }

    int ans = 0;

    cout<<max({ans,dfs(1,0,k),dfs(1,1,k),dfs(1,2,k)});;

    return 0;

}