#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  int sum = 0;
  cin >> n;
  char a[n + 5];
  int c[n + 5];
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    if (a[i] == 'R')
      c[i] = 0;
    else if (a[i] == 'G')
      c[i] = 1;
    else if (a[i] == 'B')
      c[i] = 2;
  }
  for (int i = 1; i <= n; i++) {
    if (a[i] == a[i + 1]) {
      sum++;
      ++i;
    }
  }
  cout << sum << endl;
  for (int i = 2; i <= n; i++) {
    if (c[i] == c[i - 1]) {
      if (c[i - 1] != 0 && c[i + 1] != 0)
        c[i] = 0;
      else if (c[i - 1] != 1 && c[i + 1] != 1)
        c[i] = 1;
      else if (c[i - 1] != 2 && c[i + 1] != 2)
        c[i] = 2;
    }
  }
  for (int i = 1; i <= n; i++) {
    if (c[i] == 0)
      cout << 'R';
    else if (c[i] == 1)
      cout << 'G';
    else if (c[i] == 2)
      cout << 'B';
  }
  return 0;
}
