#include <bits/stdc++.h>
using namespace std;
int main() {
  int t = 1;
  while (t--) {
    long long int n;
    cin >> n;
    string second;
    int ans = 0;
    cin >> second;
    for (int i = 1; i < n; i++) {
      if (second[i] == second[i - 1]) {
        ans++;
        if (i + 1 < n) {
          if (second[i - 1] != 'B' && second[i + 1] != 'B')
            second[i] = 'B';
          else if (second[i - 1] != 'G' && second[i + 1] != 'G')
            second[i] = 'G';
          else if (second[i - 1] != 'R' && second[i + 1] != 'R')
            second[i] = 'R';
        } else {
          if (second[i - 1] != 'B')
            second[i] = 'B';
          else if (second[i - 1] != 'G')
            second[i] = 'G';
          else if (second[i - 1] != 'R')
            second[i] = 'R';
        }
      }
    }
    cout << ans << "\n" << second << "\n";
  }
  return 0;
}
