#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  string s;
  cin >> n >> s;
  int ans = 0;
  for (int i = 1; i < n; i++) {
    if (s[i] != s[i - 1]) continue;
    if (i < n - 1) {
      for (auto c : "RGB") {
        if (c != s[i - 1] && c != s[i + 1]) {
          s[i] = c;
          ans++;
          break;
        }
      }
    } else {
      for (auto c : "RGB") {
        if (c != s[i - 1]) {
          s[i] = c;
          ans++;
          break;
        }
      }
    }
  }
  cout << ans << '\n' << s;
  return 0;
}
