WA

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned ll
#define nl "\n"
#define sz(x) x.size()
#define NumOfDigit(w) log10(w) + 1
#define fill(arr, val)  memset(arr, val , sizeof(arr))
#define PI 3.141592654
#define ceil(w, m) (((w) / (m)) + ((w) % (m) ? 1 : 0))
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define fi first
#define se second
#define cin(v) for (auto&i:v) cin >> i;
#define cout(v) for (auto&i:v) cout << i << " ";
#define fixed(n) fixed << setprecision(n)
#define MOD  1000000007


void IO(){
    ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
}
void files(){
    //freopen("filename.in" , "r" ,stdin);
            #ifndef ONLINE_JUDGE
            freopen("input.txt", "r", stdin);  freopen("output.txt", "w", stdout);
            #endif
}
bool prime(ll n){
    if(n==2 || n==3) return true;
    if(n<2 || n%2==0  ) return false;
    for(int i=3;i<=sqrt(n);i+=2)   if(n%i==0) return false;
    return true;
}

bool cmp(pair < string , int > p1 , pair < string , int > p2){
    return p1.second > p2.second;
}


void solve(){
int n; cin >> n;
string s;   cin >> s;
int cnt=0;

for(int i=0;i<n-1;i++){
    if(s[i]==s[i+1]){
        cnt++;
      if(i == n-2 ){
          if(s[i]=='R') s[i]='G';
          else if(s[i]=='G') s[i]='R';
          else s[i]='R';
          break;
      }
                if(s[i+2]=='B' and s[i+1]=='R') s[i+1]='G' ;
                else if(s[i+2]=='R' and s[i]=='B') s[i+1]='G' ;
                else if(s[i+2]=='G' and s[i]=='R') s[i+1]='B' ;
                else if(s[i+2]=='R' and s[i]=='G') s[i+1]='B' ;
                else if(s[i+2]=='B' and s[i]=='G') s[i+1]='R' ;
                else if(s[i+2]=='G' and s[i]=='B') s[i+1]='R' ;
                else if(s[i+2]=='R' and s[i]=='R') s[i+1]='B' ;
                else if(s[i+2]=='B' and s[i]=='B') s[i+1]='G' ;
                else if(s[i+2]=='G' and s[i]=='G') s[i+1]='R' ;

    }
}
cout << cnt  << nl << s;

}


int main(){
                 IO();    //     files();


    int testCase=1;  // one test case
     //  cin >> testCase ;
 while(testCase--)
        solve();  // my code

    return 0;
}