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