#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define int long long
#define ull unsigned long long
typedef long long ll;
#define lowbit(x) ((x) & -(x))

const ll INF = 0x3f3f3f3f3f3f3f3f;
const ll mod = 1e9 + 7;
const int N = 1e6 + 5, M = 1e5 + 10;
typedef pair<int, int> PII;
double T = 1 >> 30;
// double PI = acos(-1);

int gcd(int a, int b)
{
    return b ? gcd(b, a % b) : a;
}

int lcm(int a, int b)
{
    return a / gcd(a, b) * b;
}

void solve()
{
    int i, j;

    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;

    s = '?' + s;

    int l = 1, r = 0;
    int sum = 0;
    for (i = 1; i <= n;i++)
    {
        if(l)
        {
            if(s[i]=='R')
            {
                sum++;
            }else{
                r = 1;
                l = 0;
            }
        }else{
            if(s[i]=='L')
            {
                sum++;
            }else{
                r = 0;
                l = 1;
            }
        }
    }

    int ans = max(0ll, k - sum);
    cout << ans;
}

signed main()
{
    // ios_base::sync_with_stdio(false);
    // cin.tie(nullptr);
    // cout.tie(nullptr);
    int t = 1;

    //  cin >> t;

    while (t--)
    {
        //  Case++;
        solve();
    }


    return 0;
}