#include<bits/stdc++.h>
using namespace std;

typedef long long int       ll;
typedef unsigned long long int  ull;
typedef vector<int>         vi;
typedef vector<ll>          vll;
typedef vector<vi>          vvi;
typedef pair<int,int >      pii;
typedef vector< pii >       vpii;
typedef set<int>            sti;

#define sc                  scanf
#define pf                  printf
#define sci(n)              scanf("%d",&n)
#define scl(n)              scanf("%lld",&n)
#define scf(n)              scanf("%lf",&n)
#define scs(s)              scanf("%s",s)
#define pfi(n)              printf("%d",n)
#define pfl(n)              printf("%lld",n)
#define pff(n)              cout<<n
#define line                printf("\n")
#define spc                 printf(" ")
#define loop(i,x,y)         for(int i=int(x); i<=int(y); i++)
#define rloop(i,y,x)        for(int i=int(y); i>=int(x); i--)
#define cspf(i)             printf("Case %d: ", i)
#define pb                  push_back
#define mp                  make_pair
#define ff                  first
#define ss                  second
#define all(v)              v.begin(),v.end()
#define rall(v)             v.rbegin(),v.rend()
#define read()              freopen("input.txt", "r", stdin)
#define write()             freopen("output.txt", "w", stdout)
/// Constants
#define eps                 1e-9
#define PI                  acos(-1.0)  // 3.1415926535897932

int main()
{
    int n;
    sci(n);
    string s[10],st;
    cin>>s[0];
    s[1]=s[0];
    s[2]=s[0];
    s[3]=s[0];
    s[4]=s[0];
    s[5]=s[0];
    s[6]=s[0];
    int cnt[10],c;
    loop(i,0,8) cnt[i]=0;
    //1
    loop(i,0,n-1){
        if(i%3==0){
            s[1][i]='R';
            if(s[1][i]!=s[0][i])
                cnt[1]++;
        }
        else if(i%3==1){
            s[1][i]='G';
            if(s[1][i]!=s[0][i])
                cnt[1]++;
        }
        else{
            s[1][i]='B';
            if(s[1][i]!=s[0][i])
                cnt[1]++;
        }
    }
    //2
    loop(i,0,n-1){
        if(i%3==0){
            s[2][i]='R';
            if(s[2][i]!=s[0][i])
                cnt[2]++;
        }
        else if(i%3==1){
            s[2][i]='B';
            if(s[2][i]!=s[0][i])
                cnt[2]++;
        }
        else{
            s[2][i]='G';
            if(s[2][i]!=s[0][i])
                cnt[2]++;
        }
    }
    //3
    loop(i,0,n-1){
        if(i%3==0){
            s[3][i]='G';
            if(s[3][i]!=s[0][i])
                cnt[3]++;
        }
        else if(i%3==1){
            s[3][i]='R';
            if(s[3][i]!=s[0][i])
                cnt[3]++;
        }
        else{
            s[3][i]='B';
            if(s[3][i]!=s[0][i])
                cnt[3]++;
        }
    }
    //4
    loop(i,0,n-1){
        if(i%3==0){
            s[4][i]='G';
            if(s[4][i]!=s[0][i])
                cnt[4]++;
        }
        else if(i%3==1){
            s[4][i]='B';
            if(s[4][i]!=s[0][i])
                cnt[4]++;
        }
        else{
            s[4][i]='R';
            if(s[4][i]!=s[0][i])
                cnt[4]++;
        }
    }
    //5
    loop(i,0,n-1){
        if(i%3==0){
            s[5][i]='B';
            if(s[5][i]!=s[0][i])
                cnt[5]++;
        }
        else if(i%3==1){
            s[5][i]='R';
            if(s[5][i]!=s[0][i])
                cnt[5]++;
        }
        else{
            s[5][i]='G';
            if(s[5][i]!=s[0][i])
                cnt[5]++;
        }
    }
    //6
    loop(i,0,n-1){
        if(i%3==0){
            s[6][i]='B';
            if(s[6][i]!=s[0][i])
                cnt[6]++;
        }
        else if(i%3==1){
            s[6][i]='G';
            if(s[6][i]!=s[0][i])
                cnt[6]++;
        }
        else{
            s[6][i]='R';
            if(s[6][i]!=s[0][i])
                cnt[6]++;
        }
    }
    int mn = 999999;
    loop(i,1,6){
        if(mn>cnt[i]){
            mn=cnt[i];
            st=s[i];
        }
    }
    pfi(mn);line;
    cout<<st<<endl;
    return 0;
}