https://codeforces.com/contest/1108/problem/C
/*
*@Author: STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=200000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
int ans,cnt,flag,temp;
int a[N];
char str[N];
char ansstr[N];
char tmpstr[N];
int main()
{
#ifdef DEBUG
freopen("input.in", "r", stdin);
//freopen("output.out", "w", stdout);
#endif
scanf("%d",&n);
scanf("%s",str);
//while(t--){}
char s[6][4]={"RGB","RBG","BGR","BRG","GBR","GRB"};
ans=INF;
for(int i=0;i<6;i++){
cnt=0;
for(int j=0;j<n;j++){
tmpstr[j]=s[i][j%3];
if(tmpstr[j]!=str[j])
cnt++;
}
if(cnt<ans){
tmpstr[n]='\0';
ans=cnt;
strcpy(ansstr,tmpstr);
}
}
cout << ans << endl;
cout << ansstr << endl;
//cout << "Hello world!" << endl;
return 0;
}