#include <bits/stdc++.h>
using namespace std;
static map<long long, long long> m;
bool sortbysecond(pair<int, int>& a, pair<int, int>& b) {
  return (a.second > b.second);
}
bool checksubstring(string a, string b) {
  int i = 0;
  int j = 0;
  a = a + '?';
  for (; j < b.size(); j++) {
    if (a[i] == '?') {
      return true;
    }
    if (b[j] == a[i]) {
      i++;
    } else {
      i = 0;
    }
  }
  return false;
}
long long power(long long a, long long n) {
  if (n == 0) {
    return 1;
  }
  if (n == 1) {
    return a;
  }
  if (n % 2 == 0) {
    return power(a * a, n / 2);
  } else {
    return a * (power(a * a, (n - 1) / 2));
  }
}
map<long long, long long> primefactorisation(long long n) {
  map<long long, long long> factors;
  for (long long i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      factors.insert(make_pair(i, 0));
      while (n % i == 0) {
        factors[i]++;
        n = n / i;
      }
    }
  }
  if (n > 1) {
    factors.insert(make_pair(n, 1));
  }
  return factors;
}
long long sumofdigits(long long num) {
  long long temp = num;
  long long sum = 0;
  while (temp > 0) {
    sum = sum + (temp % 10);
    temp = temp / 10;
  }
  return sum;
}
long long F(long long n) {
  long long res = 1;
  for (long long i = 1; i <= n; i++) res = (res * i) % 1000000007;
  return res;
}
void solve() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int ctr = 0;
  int size = s.size();
  s = '?' + s + '?';
  for (int i = 1; i <= size; i++) {
    if (s[i] == s[i - 1]) {
      s[i] = 'R';
      if ((s[i] == s[i - 1]) || (s[i] == s[i + 1])) {
        s[i] = 'G';
      }
      if ((s[i] == s[i - 1]) || (s[i] == s[i + 1])) {
        s[i] = 'B';
      }
      ctr++;
    }
  }
  cout << ctr << '\n';
  for (int i = 1; i <= size; i++) {
    cout << s[i];
  }
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  long long t = 1;
  while (t--) solve();
}
