#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c = 0;
  cin >> n;
  string s;
  cin >> s;
  char a[3] = {'R', 'B', 'G'};
  for (int i = 1; i < s.size(); i++) {
    if (s[i] == s[i - 1] && s[i] == s[i + 1]) {
      for (int j = 0; j <= 2; j++) {
        if (s[i] != a[j]) {
          c++;
          s[i] = a[j];
          break;
        }
      }
    }
  }
  for (int i = 1; i < s.size(); i++) {
    if (s[i] == s[i - 1]) {
      for (int j = 0; j <= 2; j++) {
        if (s[i - 1] != a[j] && s[i + 1] != a[j]) {
          c++;
          s[i] = a[j];
          break;
        }
      }
    }
  }
  cout << c << endl;
  cout << s << endl;
  return 0;
}
