#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5, mod = 1e9 + 7, Mod = 998244353;
int main() {
  ios_base ::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, ans = 0;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 1; i < n; i++) {
    if (s[i] != s[i - 1]) continue;
    ans++;
    if (s[i] == 'R') {
      if (i == n - 1 || s[i + 1] == 'B')
        s[i] = 'G';
      else
        s[i] = 'B';
    } else if (s[i] == 'G') {
      if (i == n - 1 || s[i + 1] == 'R')
        s[i] = 'B';
      else
        s[i] = 'R';
    } else if (s[i] == 'B') {
      if (i == n - 1 || s[i + 1] == 'G')
        s[i] = 'R';
      else
        s[i] = 'G';
    }
  }
  cout << ans << '\n';
  cout << s;
}
