#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  char r, g, b;
  r = 'R';
  g = 'G';
  b = 'B';
  int n;
  cin >> n;
  string s;
  cin >> s;
  int cnt = 0;
  for (int i = 1; i < n; i++) {
    if (s[i] == s[i - 1]) {
      cnt++;
      if (s[i] == r) {
        s[i] = b;
        if (s[i + 1] == b || s[i + 1] == r) {
          s[i] = g;
        } else if (s[i + 1] == g) {
          s[i] = b;
        }
      } else if (s[i] == b) {
        s[i] = g;
        if (s[i + 1] == g || s[i + 1] == b) {
          s[i] = r;
        } else if (s[i + 1] == r) {
          s[i] = g;
        }
      } else if (s[i] == g) {
        s[i] = r;
        if (s[i + 1] == b || s[i + 1] == g) {
          s[i] = r;
        } else if (s[i + 1] == r) {
          s[i] = b;
        }
      }
    }
  }
  cout << cnt << "\n";
  cout << s;
}
