/*
;<+111===1?=1=zzzzvI==llllltttttttrrrrrrrvvwXzzzzzzzzzzzzzzzzzzzzzzzzzzzuUXwzzXXzvvvvvvvvXXwrrrrrrrrttz-_...............
:;;;;;;;;;;;<<?<+??=====lllzOtOZOtttttrrrrw0vvzzzzzzzuuuuuuuuuuuuuuuuuuuuuuXWXXXUXzzzzwwvvvwUwvvrrrrrrttt+_.............
;:;:;;;;;<<<-(<<<<?<z1?===zOOOlllttttttrrrdXvzzzzzuuuuuXWXuuuuuuuuuuuuuuuuuuuWkuUyWXvOzXzzzvvzXwvrrrrrrrttO-~......`..`.
;;;;;;;+<~(<<~(<(?<+I??==zwOOOllllltttrwOrwkZwXuzuuuuuuuuXWkZuZZuuZZuZZuuuuuuuuuuuXSI1wkzvvvvvvwXwvrrrrrtttO_~..........
;>;>>+z<(+><<+<<?<(zI?==z0OZlllllltttrwIzrrXv+OWuuuuuuuZZZZZyWWkZyZZZZyZZZZZZZZuuuuXk?wkzzzvvvvrvZXrrrrZzttto~~~..~.....
>>>>jI+wI+=1z<+==1zdZllzZOZttltltttrwVOwvzzuWXzvWuZZZZZyyyWfWWyyWWWkVVyWWVyyyyZZZZZX0zXkuuzzvvvvrrrrrrtrzdO1z>~~~~.~.~..
>??zwZwOtOOtlttOOtOXWyrdkdrrrrrrvwwVOwuXWSuZWXWyvWXyyyyyyyVVVVWHWppWWkkWkWHWVyyyyyyXkXWWkXuuuzzvvvvrrrzzOzXy?O-~~~.~~.~~
??jZzzXzw0vrvwXvvwzXqHkWHkuuzuXXZXwXXWgHWZZyWyyWWAXWWVffffWffppHWppppppppppHkpffffWWWHyyHHXZZZuXXuuuuuzOOwwZkzI~~~~~~.~.
??1?=XXXSuXXZuuuuZZXHg@WHHyXkpWWkHH@HHHVyVVVWHffffWWWHWpppWbppbHMHbppppHWpbpbHWbpWHHpHWpW@NkWHWykXWXyZyZkwwXyXWc~~~~~~~~
???=zW0WWWyyyyyyyyVVW@@@@MHpWWH@M@HHppHppfpppHpppHpppWHmHbWHbbkHH@HkbbkbHHkkkkHHkkkkkHNkHHHNWHHpppkWHWpppppkXpffk+-~~~~~
1zuwXWyVVVVWWWWHpffppWMHH@HHHbbbWH@NkpHHppppWUHbbHkbbbkbbHHHkkmkHUMMHkkkqMMHqkkkHHqqqMMqM###MHMqkkkkHWHHHkqqkqqkkWpk&J_~
OOOOOOOWffKXppWMWbbpbbkHHHHNkkkkHHHHHHHXHHHHHmXHkHHkkkkkkkkHkkgkHKXXMNHHHHHWMNHgHHHHHM#H###N##MmggggmggHHH@HHgggHHHHqbpf
=====llWfpSdHbHHMHkkkkqMHHH#MHHHHMMZXHkuV4bbHXZ?HbHqkkbkkkkHHkHWkH_?4UWHqkHHXZWMHmMMMNNMNNNNNNMgg@H@@@@MNMMMMMM@MMgqR:::
==l=lllZWWktWkHMHHNHqqqMH#H#HMHqqkHuu<4kw(dWRw>~_4pHVHbbbbbbHWD?ZWn.__?OXWHqeJ?TXWHMN#MWMNNNNNM@@@M@@@@MNMM@MNNMM#HHq2::
llll=llldWRtOWkMH##HNHmM####HN1JWHHHHH#####HHMHms~?W21ZWfppppH$.._?l_jdHH#NNMNN#MMMM##NNgNMNNM@@@MM@@MMMMMMMMNNN#M2?4R::
lllllllllZWyttWHMM####MNM####N<WH#TC<dMMMM#NaJJJ<?!.?_.._?TWWXt.`.. ~._<jMMMMNNMNmm2<1w#MMNMM@@@MM@HMNMNNMNMNNN$7MP;;=::
llllllllllOUOttZHkHMH#NNN###HHr(HN-..(MBUMMMMHWK..````````` ?7wl.````..` WUZHMMMMWM$._dM3dM@@@MMHMMMMNMMNNMN#M#<;?<:::::
tltllllllllllllttXkrVM#NNNN##HN,_~7-..(S,..+zOd'`.``.```.`````` ````````. ?+._+zXV^.(?<(Hg@MMMMMNMMMNMNNMM#6?d3;::::::::
ttltlllllllllllllltttdHNNNNN#HMBH&...-.. _~~~~.`````````````````````.``.`````___.._.-JVY=dHNNMNNMNNMNNMB6?>;;;:::::::::~
tttttllllllllllllltttdM##NNN#HMc....```````````.``.``.````.``````````````.`````.`.._....~dH#NNMNMMMM#E??>;;;;:::::::::~:
rtttttttltllllllltlttwgHMNNNN#HMx.....`.````.````````````.._```````````.``.`.``.``.`....(M#NNMMM@@M@Mz?>>;;;;:::::::::::
rrtttttttltllltttllttrmHMMNNNN#HMe_..`.`.`.``.`````.``.``````````````.`````.`.`..`....-+M#NNMM@@@@M@R?>>;;;;;;;:;:::::::
rrrrttttttttttlttttttrWHM@MNNNN#MNO--..``.`````.``.`````````.`.`.`.```.`.``````....._(WBW#M@@@@@@@M@R??>>;;;;;:;::::::::
rrrrrrttttttlttltttttrdM@@MNMNNN#MOlz1--.....`.``````.``.`.``````.`.`.``.`.......-(g9C==d#M@@@@@@@M@R?>>>>;;;;;;;;;:::::
rrrrrrrrttttttttttttrrdM@@MNNMNN#MZll==z1(-...`..`.``.`.` .... .```.`.`......-(JWH9====zMM@@@H@H@@H@0??>>>>;;;;;;;;;;::;
vvvrrrrrrrrttttttttttrwMg@MMMMMNNH0tlll===?z1+--.....`.`.`.``..`...`....-((gMHHM8=====ldHM@@@@@@@@MgR=??>>>>>>;;;;;;;;;;
vrvrrrrrrrrrrrttttrrrrrdgg@MNMMNN#Rrtllll=======WHa-.-....`..`.....-((+WHHHWyy#Il====lldM@@H@@H@@@HgR=??>>>>>>>>>;;;;;;;
vrvvrrrrrtttrtrrtrtttrrdgggMN@MNN#Krtllllllll=lldkuuXUUG&---.-((JzuuuZZZyyyyyXRlllllllld@@@@@H@@@@MgS==???>>>>>>>;>>>;>;
vrvrrrrrrrrrttrttrrrrrrdHggM#@MNN##rtttllllllllltWuuZuuuuuuuuZuZZZZZZyyyyyyyyXSllllllltWg@@@HW@@@MMg0==?????>>>>>>>>>>>>
rrrrrrrrtrrtrttrtttrtrrdHqggMHHNN#NrtttttlltlllltdkuZZZZZZZZZZZZZZyZyyyyyyyyyWRtllllltdgg@@HHW@@@MgHI==????>??>>>>>>>>>>
rrrrrrrrttttttttttttttrwHkqqHMXM##MwrttttttttttttwKuuZZZZZZZZZZZZZZZZZZZyyyyyyHAwtttttdgggmHXHqmMHqKl=?????>??>??>??>???
vvvrrrtrtttttrttttttttrwHkkkkkkWHHHkrrtttOwwwwXUuXWuuuZuZZZZZZZZZZZZZZZZZZZZyyyyyyWWyqHHHkHZdXWHMkHS===??????????>??????
rrrrrtttttrttttttttttttrWpppppRZMHHkwXUUXvvvzzzzuuuuuuuuuuuuZuuZZZZZZZZZZZZZZZZZZZZZXHHHkH0wXSXHppW7?<11zz???>>?>??>?>??
rrrrrttttttllllzz??<<?v!jyVVXWfZdHMr1wwrvvvvvzzzzzzuuuuuuuuuuuuuuuuZZZZZZZZZZZZZZZZZWHSHkSdSXdWffV%~~~~~~<-__<??<<??>???
rrrtrttttv<!````````.?...UZyXZVWwM@b` ?1OZXUUUUUUUZZXkXuuZuuuuuuZuZXXXkkXXyyWWWWWUWH9=(HHXkHXHbpff~~~.~~~~(-````.``._?<z
rrrtttz^_`````.``.``.!...jZykXdfWX@H-...._?zrrvvzzuuuuuUUuuuuuuZXUuuuuuuuuuuuuuzVOV:.(WHWqqWqkkpW>~~~~~~~~~(-.``.```.`..
*/

#include <bits/stdc++.h>
#include <functional>
#include <iomanip>
using namespace std;
	
#define int long long
#define pb push_back
#define F first
#define S second
#define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
#define rep(i,n) FOR(i,0,n)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define ve vector
#define vi vector<int>
#define vp vector<pair<int,int>>
#define vvi vector<vector<int>>

template<typename T> using pq = priority_queue<T,vector<T>,greater<T>>; 
using ll = long long;
ll INF = LLONG_MAX / 4000 - 100;
ll mod = 1e9 + 7;
int dx[] = {-1,0,1,0}, dy[] = {0,1,0,-1};
vector<ll> prime;
	
class fact {
public:
	int fmod = 1e9+7;
	vector<int> fac, inv;
	fact (int n, int Mod = 1e9+7) {
		fmod = Mod;
		fac = vector<int>(n,0);
		inv = vector<int>(n,0);
		fac[0] = 1; for (int i = 1; i < n; i++) fac[i] = fac[i-1] * i % fmod;
		for (int i = 0;i < n;i++) inv[i] = fact::POW(fac[i],fmod-2);
	}
	ll nCr(ll n, ll r) {if(n < r) return 0; return (fac[n] * inv[r] % fmod) * inv[n-r] % fmod;}
	ll POW(ll a, ll b) {ll c = 1; while (b > 0) {if (b & 1) {c = a * c%fmod;}a = a * a%fmod; b >>= 1;}return c;}
    inline int operator [] (int i) {return fac[i];}
};
	
template <class T = ll> T in() {T x; cin >> x; return (x);}
void DEBUG(vector<int> a) {for(int i=0;i<a.size();i++)cout<<a[i]<<" ";cout<<endl;}
void EMP(int x) {cout<<"!!!"<<x<<"!!!"<<endl;}
ll GCD(ll a, ll b) {ll c; while (b != 0) {c = a % b; a = b; b = c;}return a;}
ll LCM(ll a, ll b) {return (a / GCD(a, b)) * (b / GCD(a, b)) * GCD(a, b);}
ll POW(ll a, ll b) {ll c = 1; while (b > 0) {if (b & 1) {c = a * c%mod;}a = a * a%mod; b >>= 1;}return c;}
void PRI(ll n) {bool a[n + 1LL]; for (int i = 0; i < n + 1LL; i++) {a[i] = 1LL;}for (int i = 2; i < n + 1LL; i++) {if (a[i]) {prime.pb(i); ll b = i; while (b <= n) {a[b] = 0; b += i;}}}}
template <typename T> T chmin(T& a, T b) {if(a>b)a=b;return a;}
template <typename T> T chmax(T& a, T b) {if(a<b)a=b;return b;}
bool isSqrt(ll a) {return pow(sqrt(a),2) == a ? 1 : 0;}
void YesNo(bool a) {if (a) cout << "Yes"; else cout << "No"; cout << endl;}
void yesno(bool a) {if (a) cout << "yes"; else cout << "no"; cout << endl;}
void YESNO(bool a) {if (a) cout << "YES"; else cout << "NO"; cout << endl;}
double dis(int x1, int x2, int y1, int y2) {
	return sqrt((double)abs(x1-x2)*(double)abs(x1-x2)+(double)abs(y1-y2)*(double)abs(y1-y2));
}

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

	int cnt1 = 0;
	int cnt2 = 0;
	int ans = 0;
	rep (i, n-1) {
		if (s[i] == 'R' && s[i+1] == 'L') {
			cnt1++;
		}
		if (s[i] == 'L' && s[i+1] == 'R') {
			cnt2++;
		}
		if (s[i] == s[i+1]) ans++;
	}
	
	if (min({k,cnt1,cnt2}) == k) {
		cout << ans + 2 * min({k,cnt1,cnt2}) << endl;
		return 0;
	} else {
		if (cnt1 == cnt2) {
			cout << ans + 2 * min({k,cnt1,cnt2}) << endl;
			return 0;
		} else if (cnt1 > cnt2) {
			if (s[n-1] == 'L' || s[0] == 'R') ans++;
		} else {
			if (s[n-1] == 'R' || s[0] == 'L') ans++;
		}
	}

	cout << ans + 2 * min({k,cnt1,cnt2}) << endl;
}

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	solve();
}


Measured memory_bytes: 512