#include <bits/stdc++.h>
 #define ll long long
 #define ull unsigned long long
 #define pi 3.141592654
 #define NUM 1e18
 #define Mod  1'000'000'007
 #define fixed(n) fixed<<setprecision(n)
 #define cin(v) for(auto &i:v) cin >> i ;
 #define cout(v) for(auto &i:v) cout << i  <<" ";
 #define vowel(x) (x=='e'||x=='a'||x=='i'||x=='o'||x=='u')
 #define small(x) (x>=97&&x<=122)
 #define capital(x) (x>=65&&x<=90)
 #define Tolower(s) transform(s.begin(),s.end(),s.begin(),::tolower);
 #define Toupper(s) transform(s.begin(),s.end(),s.begin(),::toupper);
 #define sz(x) (int)(x.size())
 #define all(v) ((v).begin()), ((v).end())
 #define allr(v) ((v).rbegin()), ((v).rend())
 #define updmax(a,b) a=max(a,b)
 #define updmin(a,b) a=min(a,b)
 #define ceil(a,b) ((a/b)+(a%b?1:0))
 /* asc -> 1 2 3 ,des -> 3 2 1 */

 /***********************************************************************************/
 using namespace std;
 void Rofyda_Elghadban(){
  #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
   #endif
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
 }

 void solve(){
  int n,counter=0;
  cin>>n;
  string s;
  cin>>s;
  if(n==1){
    cout<<0<<"\n"<<s<<"\n";
    return;
  }
  if(n==2){
    if(s[0]==s[1]){
      cout<<1<<"\n"<<s[0];
      if(s[0]=='R'){
        cout<<"G"<<"\n";
      }else if(s[0]=='G'){
        cout<<"B"<<"\n";
      }else if(s[0]=='B'){
        cout<<"R"<<"\n";
      }
    }else if(s[0]!=s[1]){
      cout<<0<<"\n"<<s<<"\n";
    }
    return;
  }
  string t="RGB";
  sort(all(t));
  map<int,string>mp;
  string ss=s;
  while(next_permutation(t.begin(),t.end())){
    for(int i=0;i<n;i+=3){
      if(s[i]!=t[0]){
        ss[i]=t[0];
        counter++;
      }
      if(s[i+1]!=t[1]&&i+1<n-1){
        ss[i+1]=t[1];
        counter++;
      }
      if(s[i+2]!=t[2]&&i+2<n){
        ss[i+2]=t[2];
        counter++;
      }
    }
    mp[counter]=ss;
    ss=s;
    counter=0;
  }
  for(auto &i:mp){
    cout<<i.first<<"\n"<<i.second<<"\n";
    return;
  }
 }

 int main(){
  Rofyda_Elghadban();
  // int t;
  // cin>>t;
  // while(t--){
  //   solve();
  // }
  solve();
  return 0;
 }