https://codeforces.com/contest/1108/problem/D

/*
*@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--){}

    for(int j=1;j<n;j++){
        if(str[j-1]==str[j]){
            if(str[j]!='R'&&str[j+1]!='R'){
                str[j]='R';
            }else if(str[j]!='G'&&str[j+1]!='G'){
                str[j]='G';

            }else if(str[j]!='B'&&str[j+1]!='B'){
                str[j]='B';

            }
            ans++;
        }
    }
    cout << ans << endl;
    cout << str << endl;
    //cout << "Hello world!" << endl;
    return 0;
}