import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.complex, std.container, std.math, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum N = 30;

int R, B;
string S;

int ans;

void dfs(int pos, string s) {
  if (pos == N) {
    const len = cast(int)(s.length);
    bool ok = true;
    foreach (i; 0 .. len) {
      if (s[i] == 'R') {
        if (i - R >= 0) ok = ok && (s[i - R] != 'R');
        if (i + R < len) ok = ok && (s[i + R] != 'R');
      } else if (s[i] == 'B') {
        if (i - B >= 0) ok = ok && (s[i - B] != 'B');
        if (i + B < len) ok = ok && (s[i + B] != 'B');
      }
    }
    if (ok) {
      chmax(ans, len);
    }
  } else {
    if (S[pos] == 'R' || S[pos] == 'B') {
      dfs(pos + 1, s);
    }
    dfs(pos + 1, s ~ S[pos]);
  }
}

void main() {
  try {
    for (; ; ) {
      R = readInt();
      B = readInt();
      S = readToken();
      
      ans = 0;
      dfs(0, "");
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}