#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>
#include <cmath>
#include <tuple>
#include <cstdio>
#include <bitset>
#include <sstream>
#include <iterator>
#include <numeric>
#include <map>
#include <cstring>
#include <set>
#include <functional>
#include <iomanip>

using namespace std;

#define DEBUG_ //!!$BDs=P;~$K%3%a%s%H%"%&%H(B!!
#ifdef DEBUG_
#define dump(x)  cerr << #x << " = " << (x) << endl;
#else
#define dump(x)  ;
#endif

#define equals(a,b) (fabs((a)-(b)) < EPS)
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define SZ(x) ((int)(x).size())
#define pb push_back
#define eb emplace_back

//#define int long long

typedef long long LL;
typedef vector<int> VI;
typedef vector<LL> VL;
typedef vector<VI> VVI;
typedef vector<VL> VVL;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

    template <typename T>
std::string printVector(const std::vector<T> &data)
{
    std::stringstream ss;
    std::ostream_iterator<T> out_it(ss, ", ");
    ss << "[";
    std::copy(data.begin(), data.end() - 1, out_it);
    ss << data.back() << "]";
    return ss.str();
}

template <typename T>
void print_array(const T &ary, int size){
    REP(i,size){
        cout << ary[i] << " ";
    }
    cout << endl;
}

const int mod = 1e9+7;
const LL LINF = 1001002003004005006ll;
const int INF = 1001001001;
const double EPS = (1e-10);
const long double PI = 3.14159265358979323846264338327950288419716939937510582097494459230781640628620899;
int dx[] = {0,0,-1,1};
int dy[] = {-1,1,0,0};


signed main(int argc, char const *argv[])
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(12);
    string enc = "BWR";
    int N; cin >> N;
    string S; cin >> S;
    VL A(N);
    REP(i,N){
        int a = -1;
        if(S[i] == 'B') a = 0;
        if(S[i] == 'W') a = 1;
        if(S[i] == 'R') a = 2;

        A[i] = a;
    }
    VL f(N+1); // f[x]: x!を3で何回割れるか
    VL g(N+1); // g[x]: g!を3で割り切れなくなるまで割ったとき、残った整数を3で割った余り
    f[0] = 0;
    g[0] = 1;
    FOR(i,1,N+1){
        int x = i;
        int cnt = 0;
        while(x % 3 == 0){
            x /= 3;
            cnt++;
        }
        f[i] = f[i-1] + cnt;
    }

    FOR(i,1,N+1){
        int x = i;
        while(x % 3 == 0){
            x /= 3;
        }
        g[i] = (g[i-1] * (x % 3) ) % 3;
    }

    LL ans = 0;
    REP(i,N){
        LL nCi = -1;
        if(f[N-1] - f[i] - f[(N-1)-i] > 0){
            nCi = 0;
        }else{
            if(g[N-1] == 1 && g[i] * g[N-1-i] == 1) nCi = 1;
            if(g[N-1] == 1 && g[i] * g[N-1-i] == 2) nCi = 2;
            if(g[N-1] == 1 && g[i] * g[N-1-i] == 4) nCi = 1;
            if(g[N-1] == 2 && g[i] * g[N-1-i] == 1) nCi = 2;
            if(g[N-1] == 2 && g[i] * g[N-1-i] == 2) nCi = 1;
            if(g[N-1] == 2 && g[i] * g[N-1-i] == 4) nCi = 2;
        }

        ans += nCi * A[i];
        ans %= 3;
    }
    if(N%2 == 0){
        ans = (-ans+3) % 3;
    }

    cout << enc[ans] << endl;

}
#include <bits/stdc++.h>
using namespace std;

const int f[3][3] = {
    {1, 0, 0},
    {1, 1, 0},
    {1, 2, 1}
};
const int mod = 3;

int lucas(int x, int y) {
    int res = 1;
    while (x) {
        res = res * f[x % mod][y % mod] % mod;
        x /= mod, y /= mod;
    }
    return res;
}

int mp[200];
void solve() {
    mp['B'] = 0, mp['W'] = 1, mp['R'] = 2;
    int n, res = 0; cin >> n; --n;
    for (int i = 0; i <= n; ++i) {
        char c; cin >> c;
        int x = mp[c];
        res = (res + lucas(n, i) * x) % mod;
    }
    if (n & 1) res = -res;
    res = (res + mod) % mod;
    if (res == 0) putchar('B');
    if (res == 1) putchar('W');
    if (res == 2) putchar('R');
}

int main() {
    solve();
    return 0;
}