#include <iostream>
using namespace std;
int kr, kb;
char s[31];
int rec(int i, int r, int b, int c){
    if(i == 30) return c;
    if(s[i] == 'R'){
        int res = rec(i+1, r, b, c);
        if(!(r&(1<<(kr-1))))
            res = max(res, rec(i+1, (r<<1)|1, b<<1, c+1));
        return res;
    }
    else if(s[i] == 'B'){
        int res = rec(i+1, r, b, c);
        if(!(b&(1<<(kb-1))))
            res = max(res, rec(i+1, r<<1, (b<<1)|1, c+1));
        return res;
    }
    return rec(i+1, r<<1, b<<1, c+1);
}
int main(){
    cin >> kr >> kb;
    cin >> s;
    cout << rec(0, 0, 0, 0) << endl;
    return 0;
}