#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    vector<int> len(2);
    string s;
    cin >> len[0] >> len[1] >> s;
    int n = s.length(), ans = 10;
    vector<int> pos;
    for(int i = 0; i < n; ++i){
        if(s[i] != 'W') pos.emplace_back(i);
    }
    for(int mask = 0; mask < 1 << 20; ++mask){
        vector<bool> ban(n);
        for(int i = 0; i < 20; ++i){
            if(mask >> i & 1)   ban[pos[i]] = true;
        }
        string t = "";
        for(int i = 0; i < n; ++i){
            if(!ban[i]) t += s[i];
        }
        int nt = t.length();
        bool ok = true;
        for(int i = 0; i + len[0] < nt; ++i){
            if(t[i] == 'R' && t[i + len[0]] == 'R') ok = false;
        }
        for(int i = 0; i + len[1] < nt; ++i){
            if(t[i] == 'B' && t[i + len[1]] == 'B') ok = false;
        }
        if(ok)  chmax(ans, nt);
    }
    cout << ans << endl;
    
    return 0;
}