// yukicoder: No.38 赤青白ブロック
// 2019.6.30 bal4u

#include <stdio.h>

#define ST 35
#define LIM (1<<20)
int kr, kb;
char S[32], s[70];

int main()
{
	int i, j, w, ans;
	char *p, *q;
	
	scanf("%d%d", &kr, &kb);
	scanf("%s", S);
	
	ans = 0;
	i = LIM; while (i--) {
		j = i, p = S, q = s + ST, w = 0;
		while (*p) {
			while (*p == 'W') *q++ = 'W', w++, p++;
			if (*p == 'R') {
				if (j & 1) {
					if (*(q-kr) == 'R') goto done;
					*q++ = 'R';
				}
			} else {
				if (j & 1) {
					if (*(q-kb) == 'B') goto done;
					*q++ = 'B';
				}
			}
			if (!(j >>= 1)) break;
			p++;
		}
		q += 10 - w;
		if (q-s > ans) ans = q-s;
done:;
	}
	printf("%d\n", ans-ST);
	return 0;
}