#include <bits/stdc++.h>
using namespace std;
const int N = 200000 + 10;
const int MOD = 1e9 + 7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t, n, m, k, q;
int ans, cnt, flag, temp;
int a[N];
char str[N];
char ansstr[N];
char tmpstr[N];
int main() {
  scanf("%d", &n);
  scanf("%s", str);
  for (int j = 1; j < n; j++) {
    if (str[j - 1] == str[j]) {
      if (str[j] != 'R' && str[j + 1] != 'R') {
        str[j] = 'R';
      } else if (str[j] != 'G' && str[j + 1] != 'G') {
        str[j] = 'G';
      } else if (str[j] != 'B' && str[j + 1] != 'B') {
        str[j] = 'B';
      }
      ans++;
    }
  }
  cout << ans << endl;
  cout << str << endl;
  return 0;
}
