#include <bits/stdc++.h>
using namespace std;
char s[200005];
char s1[3] = {'B', 'R', 'G'};
int main() {
  int n, cnt = 0;
  scanf("%d", &n);
  scanf("%s", s);
  for (int i = 0; i < n - 1; i++) {
    if (s[i] == s[i + 1]) {
      if (i == n - 2) {
        for (int j = 0; j < 3; j++) {
          if (s1[j] != s[i]) {
            s[i + 1] = s1[j];
          }
        }
      } else {
        for (int j = 0; j < 3; j++) {
          if (s1[j] != s[i + 2] && s1[j] != s[i]) {
            s[i + 1] = s1[j];
            break;
          }
        }
      }
      cnt++;
    }
  }
  printf("%d\n", cnt);
  printf("%s\n", s);
}
