codeforce - Nice Garland

#include<bits/stdc++.h>
using namespace std;
#define fastread()(ios_base::sync_with_stdio(false),cin.tie(NULL));
#define ll long long
int main()
{
    fastread()
    int n,mx=1e9;
    string s, sub="BGR",ans;
    cin>>n>>s;
    do{
        int x=0;
        string str;
        for(int i=0;i<n;i++)
        {
            x+=(s[i]!=sub[i%3]);
            str+=sub[i%3];
        }
        if(mx>x)
        {
            mx=x;
            ans=str;
        }
    }while(next_permutation(sub.begin(),sub.end()));
    cout<<mx<<endl<<ans<<endl;
    return 0;
}