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