#include <bits/stdc++.h>
using namespace std;
const int M = 1e9 + 7;
long long fastpower(long long x, long long n, long long M) {
  if (n == 0)
    return 1;
  else if (n % 2 == 0)
    return fastpower((x * x) % M, n / 2, M);
  else
    return (x * fastpower((x * x) % M, (n - 1) / 2, M)) % M;
}
long long GCD(long long A, long long B) {
  if (B == 0)
    return A;
  else
    return GCD(B, A % B);
}
bool vowl(char c) {
  return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}
long long modInverse(long long A, long long M) {
  return fastpower(A, M - 2, M);
}
void sieve(long long N) {
  bool isPrime[N + 1];
  for (long long i = 0; i <= N; ++i) {
    isPrime[i] = true;
  }
  isPrime[0] = false;
  isPrime[1] = false;
  for (long long i = 2; i * i <= N; ++i) {
    if (isPrime[i] == true) {
      for (long long j = i * i; j <= N; j += i) isPrime[j] = false;
    }
  }
}
vector<long long> factorize(long long n) {
  vector<long long> res;
  for (long long i = 2; i * i <= n; ++i) {
    while (n % i == 0) {
      res.push_back(i);
      n /= i;
    }
  }
  if (n != 1) {
    res.push_back(n);
  }
  return res;
}
void printDivisors(long long n) {
  vector<long long> v;
  for (long long i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      if (n / i == i)
        v.push_back(i);
      else {
        v.push_back(i);
        v.push_back(n / i);
      }
    }
  }
}
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.second < b.second);
}
void print(vector<long long> v) {
  for (auto it : v) cout << it << " ";
}
long long count_one(long long n) {
  long long count = 0;
  while (n) {
    n = n & (n - 1);
    count++;
  }
  return count;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  string s;
  cin >> s;
  vector<pair<long long, string> > v1;
  string p[] = {"RGB", "RBG", "GRB", "GBR", "BRG", "BGR"};
  for (int j = 0; j < 6; j++) {
    string temp = p[j];
    for (int pos = 0; pos < 3; pos++) {
      string t = s;
      long long cnt = 0;
      for (int i = 0; i < n; i++) {
        if (t[i] != temp[(pos + i) % 3]) {
          cnt++;
          t[i] = temp[(pos + i) % 3];
        }
      }
      v1.push_back({cnt, t});
    }
  }
  sort(v1.begin(), v1.end());
  cout << v1[0].first << "\n";
  cout << v1[0].second << "\n";
  return 0;
}
