#include <bits/stdc++.h>
using namespace std;
string str;
int n, ans;
int main() {
  cin >> n >> str;
  for (int i = 1; i < n; i++) {
    if (str[i] == str[i - 1]) {
      if (str[i - 1] != 'R' && str[i + 1] != 'R')
        str[i] = 'R', ans++;
      else if (str[i - 1] != 'G' && str[i + 1] != 'G')
        str[i] = 'G', ans++;
      else if (str[i - 1] != 'B' && str[i + 1] != 'B')
        str[i] = 'B', ans++;
    }
  }
  cout << ans << '\n' << str;
}
