#include <bits/stdc++.h>
using namespace std;
const int INF = 1000000000;
const int MOD = 10007;
const int MAX = 1500;
char c[3] = {'R', 'G', 'B'};
int main() {
  int N;
  scanf("%d", &N);
  char str[200002];
  scanf("%s", str);
  int cnt = 0;
  for (int i = 1; i < N - 1; i++) {
    if (str[i] == str[i - 1]) {
      for (int j = 0; j < 3; j++) {
        if (c[j] == str[i - 1] || c[j] == str[i + 1])
          continue;
        else {
          cnt++;
          str[i] = c[j];
          break;
        }
      }
    }
  }
  if (str[N - 1] == str[N - 2]) {
    for (int j = 0; j < 3; j++) {
      if (c[j] == str[N - 2])
        continue;
      else {
        cnt++;
        str[N - 1] = c[j];
        break;
      }
    }
  }
  printf("%d\n%s\n", cnt, str);
  return 0;
}
