#include <bits/stdc++.h>
using namespace std;
void _print(long long t) { cerr << t; }
void _print(int t) { cerr << t; }
void _print(string t) { cerr << t; }
void _print(char t) { cerr << t; }
void _print(long double t) { cerr << t; }
void _print(double t) { cerr << t; }
void _print(unsigned long long t) { cerr << t; }
template <class T, class V>
void _print(pair<T, V> p);
template <class T>
void _print(vector<T> v);
template <class T>
void _print(vector<vector<T>> v);
template <class T>
void _print(set<T> v);
template <class T, class V>
void _print(map<T, V> v);
template <class T>
void _print(multiset<T> v);
template <class T, class V>
void _print(pair<T, V> p) {
  cerr << "{";
  _print(p.first);
  cerr << ",";
  _print(p.second);
  cerr << "}";
}
template <class T>
void _print(vector<T> v) {
  cerr << "[ ";
  for (T i : v) {
    _print(i);
    cerr << " ";
  }
  cerr << "]";
}
template <class T>
void _print(vector<vector<T>> v) {
  cerr << "==>" << endl;
  for (vector<T> vec : v) {
    for (T i : vec) {
      _print(i);
      cerr << " ";
    }
    cerr << endl;
  }
}
template <class T>
void _print(set<T> v) {
  cerr << "[ ";
  for (T i : v) {
    _print(i);
    cerr << " ";
  }
  cerr << "]";
}
template <class T>
void _print(multiset<T> v) {
  cerr << "[ ";
  for (T i : v) {
    _print(i);
    cerr << " ";
  }
  cerr << "]";
}
template <class T, class V>
void _print(map<T, V> v) {
  cerr << "[ ";
  for (auto i : v) {
    _print(i);
    cerr << " ";
  }
  cerr << "]";
}
mt19937_64 rang(
    chrono::high_resolution_clock::now().time_since_epoch().count());
int rng(int lim) {
  uniform_int_distribution<int> uid(0, lim - 1);
  return uid(rang);
}
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7;
long long mod_exp(long long a, long long b) {
  a %= mod;
  if (a == 0) return 0LL;
  long long res = 1LL;
  while (b > 0) {
    if (b & 1) res = (res * a) % mod;
    a = (a * a) % mod;
    b >>= 1;
  }
  return res;
}
long long mod_inv(long long a) { return mod_exp(a, mod - 2); }
long long GCD(long long a, long long b) { return (b == 0) ? a : GCD(b, a % b); }
void solve() {
  int n;
  string s;
  cin >> n >> s;
  int cnt = 0;
  for (int i = 0; i < n; i++) {
    int j = i;
    while (j < n and s[i] == s[j]) j += 1;
    string col = "RGB";
    col.erase(col.find(s[i]), 1);
    if (j < n) col.erase(col.find(s[j]), 1);
    for (int k = i + 1; k < j; k += 2) {
      s[k] = col[0];
      cnt += 1;
    }
    i = j - 1;
  }
  cout << cnt << "\n" << s << "\n";
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
  srand(chrono::high_resolution_clock::now().time_since_epoch().count());
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
