#include <bits/stdc++.h>
using namespace std;
int n, ans = 0;
char s[3] = {'G', 'B', 'R'};
string str;
int main() {
  cin >> n >> str;
  for (int i = 1; i < str.size(); i++) {
    if (str[i] == str[i - 1]) {
      for (int j = 0; j < 3; j++) {
        if (s[j] != str[i - 1] && s[j] != str[i + 1]) {
          ans++;
          str[i] = s[j];
          break;
        }
      }
    }
  }
  cout << ans << endl << str << endl;
}
