#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <vector>
#include <map>
#include <cstring>
#include <algorithm>
#include <set>
#include <fstream>
#include <sstream>
#include <string>

using namespace std;

void fail(const char* msg = NULL) {
  if (msg) {
    cout << "fail: " << msg << endl;
  } else {
    cout << "fail" << endl;
  }
  exit(1);
}

void fassert(bool cond, const char* msg = NULL) {
  if (!cond) {
    fail(msg);
  }
}

struct input {
  input(FILE* f) : uch(-2), fin(f), sin(NULL), read_bytes(0) {
  }
  input(istream& in) : uch(-2), fin(NULL), sin(&in), read_bytes(0) {
  }

  int get() {
    if (uch != -2) {
      int ch = uch;
      uch = -2;
      return ch;
    } else if (fin) {
      read_bytes++;
      return fgetc(fin);
    }
    return sin->get();
  }

  void unget(int ch) {
    uch = ch;
  }

  char get_char() {
    int ch = get();
    if (ch == -1) {
      fail("expected char");
    } else if (ch != '\n' && (ch < 32 || 126 < ch)) {
      fail("expected printable ascii");
    }
    return ch;
  }

  void get_eof() {
    fassert(get() == -1, "expected eof");
  }

  void get_eol() {
    fassert(get() == '\n', "expected eol");
  }

  void get_space() {
    fassert(get() == ' ', "expected space");
  }

  void get_spaces() {
    int ch;
    get_space();
    for (ch = get(); ch == ' '; ch = get());
    unget(ch);
  }

  string get_token() {
    int ch;
    string res;
    for (ch = get(); ch != -1 && ch != '\n' && ch != ' '; ch = get()) {
      res += (char)ch;
    }
    fassert(!res.empty(), "expected token");
    unget(ch);
    return res;
  }

  long long get_int(long long min, long long max, const char* msg = NULL) {
    string tok = get_token();
    long long res = atoll(tok.c_str());
    fassert(tok == to_string(res), "expected int");
    if(msg)
      fassert(min <= res && res <= max, msg);
    else
      fassert(min <= res && res <= max, "int out of range");
    return res;
  }

  double get_double(double min, double max, const char* msg = NULL) {
    string tok = get_token();
    double res = atof(tok.c_str());
    if(msg)
      fassert(min <= res && res <= max, msg);
    else
      fassert(min <= res && res <= max, "double out of range");
    return res;
  }

  string get_line(int min_length, int max_length, const char* lmsg = NULL, const char* gmsg = NULL) {
    int ch;
    string res;
    for (ch = get(); ch != -1 && ch != '\n'; ch = get()) {
      res += (char)ch;
      if((int)res.size() > max_length) {
        if(gmsg) fail(gmsg);
        else fail("line too long");
      }
    }
    if((int)res.size() < min_length) {
      if(lmsg) fail(lmsg);
      else fail("line too short");
    }
    unget(ch);
    return res;
  }

  int uch;
  FILE* fin;
  istream* sin;
  int read_bytes;
};

int main(int argc, char** argv) {
  input in(cin);

  string s = in.get_line(1, 100000, "string length too short", "string length too long");
  in.get_eol();
  in.get_eof();
  for(int i = 0; i < (int)s.length(); i++) {
    fassert(s[i] == 'B' || s[i] == 'R', "character inside is not B or R");
  }
  return 42;
}