#include <bits/stdc++.h>
using namespace std;
inline long long add(long long x, long long y) {
  x += y;
  if (x >= 1000000007) x -= 1000000007;
  return x;
}
inline long long sub(long long x, long long y) {
  x -= y;
  if (x < 0) x += 1000000007;
  return x;
}
inline long long mul(long long x, long long y) {
  return ((x % 1000000007) * (y % 1000000007)) % 1000000007;
}
inline long long pwr(long long a, long long b) {
  long long x = 1LL;
  while (b) {
    if (b & 1) x = mul(x, a);
    a = mul(a, a);
    b >>= 1;
  }
  return x;
}
bool CHK(long long n) {
  if (n == 1) return 0;
  if (n == 2 or n == 3) return 1;
  if (n % 2 == 0 or n % 3 == 0) return 0;
  for (long long i = 5; i * i <= n; i += 6)
    if (n % i == 0 or n % (i + 2) == 0) return 0;
  return 1;
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL);
  long long n = 0;
  cin >> n;
  string s;
  cin >> s;
  long long cnt = 0;
  for (long long i = 0; i < n - 1; i++) {
    if (s[i] == '*') continue;
    if (s[i] == s[i + 1]) cnt++, s[i + 1] = '*';
  }
  cout << cnt << "\n";
  for (long long i = 0; i < n; i++) {
    if (s[i] == '*' and i != n - 1) {
      if (s[i - 1] == 'R' and s[i + 1] == 'G')
        s[i] = 'B';
      else if (s[i - 1] == 'G' and s[i + 1] == 'B')
        s[i] = 'R';
      else if (s[i - 1] == 'R' and s[i + 1] == 'B')
        s[i] = 'G';
      else if (s[i - 1] == 'R' and s[i + 1] == 'R')
        s[i] = 'G';
      else if (s[i - 1] == 'B' and s[i + 1] == 'B')
        s[i] = 'G';
      else if (s[i - 1] == 'G' and s[i + 1] == 'G')
        s[i] = 'R';
      else if (s[i - 1] == 'G' and s[i + 1] == 'R')
        s[i] = 'B';
      else if (s[i - 1] == 'B' and s[i + 1] == 'G')
        s[i] = 'R';
      else if (s[i - 1] == 'B' and s[i + 1] == 'R')
        s[i] = 'G';
    } else if (s[i] == '*' and i == n - 1) {
      if (s[i - 1] == 'R')
        s[i] = 'G';
      else if (s[i - 1] == 'B')
        s[i] = 'G';
      else if (s[i - 1] == 'G')
        s[i] = 'B';
    }
  }
  for (auto u : s) cout << u;
  return 0;
}
