#include <bits/stdc++.h>
#define For(i, a, b) for(int (i)=(int)(a); (i)<(int)(b); ++(i))
#define rFor(i, a, b) for(int (i)=(int)(a)-1; (i)>=(int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<lint, lint> pll;
template<class T> bool chmax(T &a, const T &b){if(a<b){a=b; return true;} return false;}
template<class T> bool chmin(T &a, const T &b){if(a>b){a=b; return true;} return false;}
template<class T> T div_floor(T a, T b){
    if(b < 0) a *= -1, b *= -1;
    return a>=0 ? a/b : (a+1)/b-1;
}
template<class T> T div_ceil(T a, T b){
    if(b < 0) a *= -1, b *= -1;
    return a>0 ? (a-1)/b+1 : a/b;
}

constexpr lint mod = 1e9+7;
constexpr lint INF = mod * mod;
constexpr int MAX = 200010;

int a, b, ans = 0;
string s, t;

void dfs(int cur){
    if(cur == s.size()){
        chmax(ans, (int)t.size());
        return;
    }
    if(s[cur] == 'W'){
        t += 'W';
        dfs(cur+1);
        t.pop_back();
    }
    else{
        dfs(cur+1);
        if(s[cur] == 'R'){
            if(cur-a < 0 || *(t.end()-a) != 'R'){
                t += 'R';
                dfs(cur+1);
                t.pop_back();
            }
        }
        else{
            if(cur-b < 0 || *(t.end()-b) != 'B'){
                t += 'B';
                dfs(cur+1);
                t.pop_back();
            }
        }
    }
}

int main(){
    cin >> a >> b >> s;
    dfs(0);
    printf("%d\n", ans);
}