#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n >> s;
  int ans = 0;
  string base = "RGB";
  for (int i = 1; i < n; i++) {
    if (s[i - 1] == s[i]) {
      ans++;
      for (int j = 0; j < 3; j++) {
        if (s[i - 1] != base[j] && (i + 1 == n || s[i + 1] != base[j])) {
          s[i] = base[j];
          break;
        }
      }
    }
  }
  cout << ans << endl;
  cout << s << endl;
}
