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#include <bits/stdc++.h>
using namespace std ;
#define For(n) for(long long i = 0; i < n; i++)
#define endl '\n'
#define int long long
char next (char c){
    if(c == 'R')return 'B';
    if(c == 'B')return 'G';
    return 'R';
}
 
void solve (){
    int n;cin>>n;
    string s;cin>>s;
    if(n==1||(n==2 && s[0]!=s[1])){
        cout << 0 << endl << s << endl;
        return;
    }
    else if(n==2){
        cout << 1 << endl<<s[0]<<next(s[0])<< endl; 
        return;
    }
    int cnt = 0;
    for(int i =0 ;i +2 < n ; i++){
        if(i>0){
            if(s[i+2]!=s[i-1])cnt++;
            s[i+2] = s[i-1];
        }
        else if(s[i] == s[i+1] && s[i] ==s[i+2]){
            cnt+=2;
            if(i+3<n) s[i] = s[i+3];
            if(i+4<n) s[i+1] = s[i+4];
            while(s[i] == s[i+1])
                s[i+1] = next(s[i+1]);
            while(s[i+1] == s[i+2] || s[i+2] == s[i])
                s[i+2]= next(s[i+2]);
        }
        else if(s[i] == s[i+1] ){
            cnt ++;
            while(s[i+1]==s[i]|| s[i+1]==s[i+2])
                s[i] = next(s[i]);
        }
        else if(s[i] == s[i+2]){
            cnt ++;
            while(s[i+2]==s[i]|| s[i+1]==s[i+2])
                s[i+2] = next(s[i+2]);            
        }
        else if(s[i+1] == s[i+2]){
            cnt ++;
            while(s[i+2]==s[i]|| s[i+1]==s[i+2])
                s[i+2] = next(s[i+2]);             
        }
    }
        cout << cnt << endl;
        cout << s << endl;
    
}
 
signed main ()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);    
    int t =1;
    // cin>>t;
    while (t--){
        solve();
    }    
}