#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;
  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";
      cout<<s[0];
      if(s[0]=='R'){
        cout<<"G"<<"\n";
      }else if(s[0]=='B'){
        cout<<"R"<<"\n";
      }else if(s[0]=='G'){
        cout<<"B"<<"\n";
      }
    }else{
      cout<<0<<"\n"<<s<<"\n";
    }
    return;
  }
  int rgb=0,rbg=0,bgr=0,brg=0,grb=0,gbr=0;
  string rgbs=s,rbgs=s,bgrs=s,brgs=s,grbs=s,gbrs=s;
  /*rgb*/
  map<int,string>mp;
  for(int i=0;i<n;i+=3){
    if(s[i]!='R'){
      rgbs[i]='R';
      rgb++;
    }
    if(s[i+1]!='G'&&i+1<n-1){
      rgbs[i+1]='G';
      rgb++;
    }
    if(s[i+2]!='B'&&i+2<n){
      rgbs[i+2]='B';
      rgb++;
    }
  }
  mp[rgb]=rgbs;
  /*rbg*/
  for(int i=0;i<n;i+=3){
    if(s[i]!='R'){
      rbgs[i]='R';
      rbg++;
    }
    if(s[i+1]!='B'&&i+1<n-1){
      rbgs[i+1]='B';
      rbg++;
    }
    if(s[i+2]!='G'&&i+2<n){
      rbgs[i+2]='G';
      rbg++;
    }
  }
  mp[rbg]=rbgs;
  /*bgr*/
  for(int i=0;i<n;i+=3){
    if(s[i]!='B'){
      bgrs[i]='B';
      bgr++;
    }
    if(s[i+1]!='G'&&i+1<n-1){
      bgrs[i+1]='G';
      bgr++;
    }
    if(s[i+2]!='R'&&i+2<n){
      bgrs[i+2]='R';
      bgr++;
    }
  }
  mp[bgr]=bgrs;
  /*brg*/
  for(int i=0;i<n;i+=3){
    if(s[i]!='B'){
      brgs[i]='B';
      brg++;
    }
    if(s[i+1]!='R'&&i+1<n-1){
      brgs[i+1]='R';
      brg++;
    }
    if(s[i+2]!='G'&&i+2<n){
      brgs[i+2]='G';
      brg++;
    }
  }
  mp[brg]=brgs;
  /*grb*/
  for(int i=0;i<n;i+=3){
    if(s[i]!='G'){
      grbs[i]='G';
      grb++;
    }
    if(s[i+1]!='R'&&i+1<n-1){
      grbs[i+1]='R';
      grb++;
    }
    if(s[i+2]!='B'&&i+2<n){
      grbs[i+2]='B';
      grb++;
    }
  }
  mp[grb]=grbs;
  /*gbr*/
  for(int i=0;i<n;i+=3){
    if(s[i]!='G'){
      gbrs[i]='G';
      gbr++;
    }
    if(s[i+1]!='B'&&i+1<n-1){
      gbrs[i+1]='B';
      gbr++;
    }
    if(s[i+2]!='R'&&i+2<n){
      gbrs[i+2]='R';
      gbr++;
    }
  }
  mp[gbr]=gbrs;
  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;
 }