#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll I=1167167167167167167;
ll Q=1e9+7;
#define rep(i,a) for (ll i=0;i<a;i++)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
template<class T> void print_tate(vector<T> &v) {rep(i,v.size()) cout<<v[i]<<"\n";}
void yneos(bool a){if(a) cout<<"Yes"<<"\n"; else cout<<"No"<<"\n";}

//おちこんだりもしたけれど、私はげんきです。
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	ll N;
	cin>>N;
	vector<ll> fib={1,1};
	int k=1;
	while(fib[k]+fib[k-1]<=N){
		fib.push_back(fib[k]+fib[k-1]);
		k++;
	}
	int M=fib.size();
	vector<int> c(M);
	for(int i=M-1;i>0;i--){
		while(N>=fib[i]){
			c[i]++;
			N-=fib[i];
		}
	}
	vector<ll> ans;
	for(int i=1;i<M;i++){
		int a=1,b=4;
		if((M-i)%2==1){
			a=2;
			b=3;
		}
		rep(j,c[M-i]) ans.push_back(a);
		ans.push_back(b);
	}
	cout<<ans.size()<<"\n";
	rep(i,ans.size()){
		cout<<ans[i]<<"\n";
	}
	
	/*ll X=0,Y=0;
	rep(i,ans.size()){
		if(ans[i]==1) X++;
		if(ans[i]==2) Y++;
		if(ans[i]==3) X+=Y;
		if(ans[i]==4) Y+=X;
		cout<<X<<" "<<Y<<endl;
	}*/
}

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for (int i = 0; i < (int)(n) ; i++)

vector<ll> to_base3(ll n) {
    if(n==0) return vector<ll>{0};
    vector<ll> ret;
    while(n>0) {
        ret.push_back(n%3);
        n/=3;
    }
    return ret;
}
ll subcom(ll a, ll b) {
    if(a==0) {
        if(b==0) return 1;
        return 0;
    }
    if(a==1) {
        if(b==2) return 0;
        return 1;
    }
    else {
        if(b==0 || b==2) return 1;
        return 2;
    }
}
ll com(ll a, ll b) { // Lucasの定理
    if(a<b) return 0;

    ll ret=1;
    auto v=to_base3(a);
    auto w=to_base3(b);
    for(int i=0; i<(int)min(v.size(), w.size()); i++) {
        ret *= subcom(v[i], w[i]);
        ret %= 3;
    }
    return ret;
}


int main() {
    ll n; cin>>n;
    vector<ll> bottom(n);
    rep(i, n) {
        char t; cin>>t;
        if(t=='R') bottom[i]=0;
        else if(t=='B') bottom[i]=1;
        else bottom[i]=2;
    }
    ll ans=0;
    for(int i=0; i<=n-1; i++) {
        ans = (ans+bottom[i]*com(n-1, i))%3;
    }

    if((n-1)%2==1) ans = (3-ans)%3;
    
    if(ans==0) cout << 'R' << endl;
    else if(ans==1) cout << 'B' << endl;
    else cout << 'W' << endl;
}