#include <bits/stdc++.h>
using namespace std;
const long long MAX = 2e5 + 10;
int n;
string s, xx = "RGB";
int getID(char c) {
  if (c == 'R')
    return 1;
  else if (c == 'G')
    return 2;
  return 3;
}
int last[4];
int dp[MAX][4][4][4];
int mn = 1e9;
vector<char> v, ans;
int tokyoGhoul(int cur, int cnt) {
  if (cur == n) {
    if (cnt < mn) {
      mn = cnt;
      ans = v;
    }
    return cnt;
  }
  int &ret = dp[cur][last[0]][last[1]][last[2]];
  if (~ret) return ret;
  ret = 1e18;
  for (int i = 0; i < xx.size(); i++) {
    int id = getID(xx[i]);
    int prev = last[id];
    char ch = xx[i];
    if (prev == -1 || (cur - prev) != 1) {
      v.push_back(ch);
      last[id] = cur;
      if (xx[i] != s[cur])
        ret = min(ret, tokyoGhoul(cur + 1, cnt + 1));
      else
        ret = min(ret, tokyoGhoul(cur + 1, cnt));
      last[id] = prev;
      v.pop_back();
    }
  }
  return ret;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> s;
  vector<string> vv;
  int cnt = 0, cnt2 = 0;
  string s1 = "", s2 = "";
  for (int j = 0; j < 3; j++) {
    cnt = 0, s1 = "";
    s1 += xx[j];
    if (s[0] != s1[0]) cnt++;
    for (int i = 1; i < n; i++) {
      if (s[i] == s1[i - 1]) {
        cnt++;
        bool f = 1;
        for (int j = 0; j < xx.size(); j++) {
          if (s1[i - 1] != xx[j] && (i + 1 == n || s[i + 1] != xx[j])) {
            s1 += xx[j];
            f = 0;
            break;
          }
        }
        if (f)
          for (int j = 0; j < xx.size(); j++) {
            if (s[i - 1] != xx[j]) {
              s1 += xx[j];
              break;
            }
          }
      } else
        s1 += s[i];
    }
    if (cnt < mn) {
      mn = cnt;
      s2 = s1;
    }
  }
  cout << mn << endl;
  for (auto i : s2) cout << i;
  cout << endl;
}
