#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h" // define macro "/D__MAI"

using namespace std;
typedef long long int ll;

#define debugv(v) printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;
#define debugm(m) printf("L%d %s is..\n",__LINE__,#m);for(auto v:m){for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) printf("L%d %s is => ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;
#define debugaa(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[x][y]<<" ";}cout<<endl;}
#define debugaar(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}
#define ALL(v) (v).begin(),(v).end()
#define repeat(l) for(auto cnt=0;cnt<(l);++cnt)
#define iterate(b,e) for(auto cnt=(b);cnt!=(e);++cnt)
#define MD 1000000007ll
#define PI 3.1415926535897932384626433832795
template<typename T1, typename T2>
ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }

#define TIME chrono::system_clock::now()
#define MILLISEC(t) (chrono::duration_cast<chrono::milliseconds>(t).count())
namespace {
    std::chrono::system_clock::time_point ttt;
    void tic() { ttt = TIME; }
    void toc() { fprintf(stderr, "TIME : %lldms\n", MILLISEC(TIME - ttt)); }
    std::chrono::system_clock::time_point tle = TIME;
#ifdef __MAI
    void safe_tle(int msec) { assert(MILLISEC(TIME - tle) < msec); }
#else
#define safe_tle(k) ;
#endif
}

#ifdef __MAI
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
#ifdef __VSCC
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#endif
namespace {
#define isvisiablechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T>
        void input_integer(T& var) {
            var = 0;
            T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc&&cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var*sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) {
            input_integer<int>(var);
            return *this;
        }
        inline MaiScanner& operator>>(long long& var) {
            input_integer<long long>(var);
            return *this;
        }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiablechar(cc); cc = getchar_unlocked());
            for (; isvisiablechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
        }
    };
}
MaiScanner scanner;


int rr, bb;

int dfs(const string&);


unordered_map<string, int> memo[32];

int pick(string state,int idx) {
    state.erase(idx, 1);
    int size = state.size();
    if (memo[size].count(state)) return memo[size][state];
    return memo[size][state] = dfs(state);
}

int dfs(const string& state) {
    int best = -1;

    bool failure = false;
    {
        int i = 0;
        // int last_r = -1;
        // int last_b = -1;
        for (; i < state.size() - 1;++i) {

            int lookup_r = min(i + rr, (int)state.size() - 1);
            int lookup_b = min(i + bb, (int)state.size() - 1);

            if (state[i] == 'R' && state[lookup_r] == 'R') {
                // if (last_r != i) best = max(best, pick(state, i));
                // best = max(best, pick(state, lookup_r));
                // last_r = lookup_r;
                failure = true;
                break;
            }
            if (state[i] == 'B' && state[lookup_b] == 'B') {
                // if (last_b != i) best = max(best, pick(state, i));
                // best = max(best, pick(state, lookup_b));
                // last_b = lookup_b;
                failure = true;
            }
        }
    }
    if (failure == true) {
        for (int i = 0; i < state.size() - 1; ++i) {
            if (state[i] == 'R' || state[i] == 'B') {
                best = max(best, pick(state, i));
            }
        }
        return best;
    }
    else {
        return state.size() - 1;
    }
    // if (best == -1) {
    //     return state.size() - 1;
    // }
    // else {
    //     return best;
    // }
}


int main() {

    cin >> rr >> bb;
    
    string str;
    cin >> str;

    str.push_back('$');


    cout << dfs(str) << endl;


    return 0;
}