#include<bits/stdc++.h>
//#include <boost/multiprecision/cpp_int.hpp>
//using namespace boost::multiprecision;

#define ll long long int
#define ld long double
#define bigint int64_t
#define vll vector<ll>
#define vpll vector<pair<ll,ll>>
#define mp make_pair
#define pb push_back
#define MOD 1000000007
#define flash ios_base::sync_with_stdio(false);cin.tie(NULL);
#define test ll t;read(t);while(t--)
#define all(v) v.begin(),v.end()
#define pll pair<ll,ll>

/*#include <ext/pb_ds/assoc_container.hpp> // Policy_based_Data_Structure 
#include <ext/pb_ds/graph_policy.hpp> 
using namespace __gnu_pbds;*/ 

#define forn(i,n) for(ll (i) = 0 ; (i) < (n) ; ++(i))
#define for1(i,n) for(ll (i) = 1 ; (i) <= (n) ; ++(i))
#define forr(i,n) for(ll (i) = (n)-1 ; (i)>=0 ; --(i))
#define forab(i,a,b,c) for(ll (i) = a ; (i) <= (b) ; (i)+=(c))

using namespace std;
template <typename T>
void read(T &x){
    cin >> x;
}
template <typename T , typename T0>
void read(T &x,T0 &y){
    cin >> x >> y;
}

template <typename T , typename T0 , typename T1>
void read(T &x,T0 &y,T1 &z){
    cin >> x >> y >> z;
}

template <typename T , typename T0 , typename T1 , typename T2>
void read(T &x,T0 &y,T1 &z,T2 &w){
    cin >> x >> y >> z >> w;
}

template <typename T , typename T0>
void read(pair< T , T0 > &p){
    cin >> p.fst >>p.scd;
}

template <typename T>
void read(vector< T > &oneD,ll n){
    forn(i,n)
    {
        ll x;
        read(x);
        oneD.push_back(x);
    }
}

template <typename T>
void read(T oneD[] , ll n){
    for(ll i=0;i<n;i++){
        read(oneD[i]);
    }
}

template <typename T>
void write(T &x){
    cout << x << " ";
}

template <typename T , typename T0>
void write(T &x,T0 &y){
    cout << x << " " << y << "\n";
}

template <typename T , typename T0 , typename T1>
void write(T &x,T0 &y,T1 &z){
    cout << x << " " << y << " " << z << "\n";
}

template <typename T , typename T0 , typename T1 , typename T2>
void write(T &x,T0 &y,T1 &z,T2 &w){
    cout << x << " " << y << " " << z << " " << w << "\n";
}

template <typename T , typename T0>
void write(pair< T , T0 > &p){
    write(p.fst);
    write(p.scd);
    cout << endl;
}

template <typename T>
void write(vector< T > &oneD){
    for(ll i=0;i<oneD.size();i++){
        write(oneD[i]);
    }
    cout << endl;
}

template <typename T>
void write(T oneD[] ,int n){
    for(ll i=0;i<n;i++){
        write(oneD[i]);
    }
    cout << endl;
}

template <typename T , typename T0>
void write(map< T , T0 > &mpp){
    for(auto it : mpp){
        write(it.fst);
        cout << ": ";
        write(it.scd);
        cout << "\n";
    }
    cout<<endl;
}

vll seive;
void Seive(){
    const ll maxn = 3000005;
    seive.resize(maxn);
    forn(i,maxn) seive[i] = i;
    seive[1] = -1;
    seive[0] = -1;
    forab(i,2,maxn,1) if(i == seive[i]) for(ll j = 2*i ; j < maxn ; j+=i) if(seive[j] == j) seive[j] = i;
}

ll extended_GCD(ll a , ll b , ll &x , ll &y){
    if(a == 0){
        x = 0;
        y = 1;
        return b;
    }
    ll x1 , y1;
    ll gcd = extended_GCD(b%a , a , x1 , y1);
    x = y1 - (b/a)*x1; 
    y = x1;
    return gcd;
}

ll modinv(ll a , ll mod = MOD){
    ll x , y;
    extended_GCD(a , mod , x , y);
    if(x < 0) x += mod;
    return x;
}

//Chinese Remainder Theoram
ll find_x_CRT(ll num[],ll rem[],ll n)
{
    ll pro=1;
    forn(i,n)
    pro*=num[i];
    ll res=0;
    forn(i,n)
    {
        ll pp = pro/num[i];
        res+=(rem[i]*modinv(pp,num[i])*pp);
    }
    res%=pro;
    return res;
}

ll power(ll a, ll b, ll m = MOD) {
    a%=m;
    ll res = 1;
    while (b > 0) {
        if (b & 1)
            res = res * a %m;
        a = a * a %m;
        b >>= 1;
    }
    return res;
}

ll powe(ll a, ll b, ll m = MOD) {
    ll res = 1;
    while (b > 0) {
        if (b & 1)
            res = res * a;
        a = a * a;
        b >>= 1;
    }
    return res;
}

ll gcd(ll a, ll b)
{
    if (a == 0)
        return b;
    return gcd(b % a, a);
}

string getString(char x) 
{ 
    string s(1, x); 
    return s;    
} 

//typedef graph<ll, null_type, less<ll>, rb_graph_tag,graph_order_bigsmallistics_node_update> index_set

//Graph basic template
void add_edge(ll u,ll v,vector<vector<ll>> &ad)
{
    ad[u].pb(v);
    ad[v].pb(u);
}
/*const ll maxn = 2e5+5;
// Unweighted Graph
vector<vector<ll>> ad(maxn);
vector<bool> vis(maxn);
void add_edge(ll u,ll v,vector<vector<ll>> &ad)
{
    ad[u].pb(v);
    ad[v].pb(u);
}*/
bool mycomp(pll &a,pll &b)
{
    return a.second<b.second;
}

int main ()
{
    flash;
    ll n,k;
    read(n,k);
    string s;
    read(s);
    ll change[n]={};
    forab(i,1,(n-1),1)
    {
        ll z = 0;
        if(s[i]!=s[i-1])
        z=1;
        if(z!=change[i-1])
        {
            change[i]=1;
        }
    }
    /*forn(i,n)
    cout<<change[i]<<" ";
    cout<<"\n";*/
    priority_queue<pll> q;
    ll sum = 0,st=0;
    forn(i,n)
    {
        if(change[i]==0)
        {
            if(sum!=0)
            {
                q.push({sum,st});
            }
            sum=0;
        }
        else
        {
            if(sum==0)
            {
                st = i;
            }
            sum++;
        }
    }
    if(change[n-1])
    {
    if(sum!=0)
    {
        q.push({sum,st});
    }
    }
    vpll fin;
    while(!q.empty())
    {
        pll y = q.top();
        q.pop();
        fin.pb(y);
    }
    sort(fin.begin(),fin.end(),mycomp);
    /*for(auto x:fin)
    cout<<x.first<<" "<<x.second<<"\n";*/
    for(auto x:fin)
    {
        pll y = x;
        k--;
        forab(i,y.second,(y.second+y.first-1),1)
        {
            if(s[i]=='L')
            s[i]='R';
            else
            {
                s[i]='L';
            }
        }
        if(k==0)
        break;
    }
    /*while(!q.empty()&&k>0)
    {
        pll y = q.top();
        q.pop();
        k--;
        forab(i,y.second,(y.second+y.first-1),1)
        {
            if(s[i]=='L')
            s[i]='R';
            else
            {
                s[i]='L';
            }
        }
    }*/
    ll ans = 0;
    forn(i,n)
    {
        if(i!=0)
        {
            if(s[i]==s[i-1])
            ans++;
        }
    }
    cout<<ans;
    return 0;
}

Measured memory_bytes: 3524