#include <bits/stdc++.h>
using namespace std;
int a[200000 + 5], b[10][200000 + 5];
int main() {
  int n, i;
  cin >> n;
  char c;
  c = getchar();
  for (i = 1; i <= n; i++) {
    c = getchar();
    if (c == 'R') a[i] = 1;
    if (c == 'G') a[i] = 2;
    if (c == 'B') a[i] = 3;
  }
  b[1][1] = 1;
  b[1][2] = 2;
  for (i = 3; i <= n; i++) b[1][i] = 6 - b[1][i - 1] - b[1][i - 2];
  for (i = 1; i <= n; i++)
    if (b[1][i] != a[i]) b[1][0]++;
  b[2][1] = 1;
  b[2][2] = 3;
  for (i = 3; i <= n; i++) b[2][i] = 6 - b[2][i - 1] - b[2][i - 2];
  for (i = 1; i <= n; i++)
    if (b[2][i] != a[i]) b[2][0]++;
  b[3][1] = 2;
  b[3][2] = 1;
  for (i = 3; i <= n; i++) b[3][i] = 6 - b[3][i - 1] - b[3][i - 2];
  for (i = 1; i <= n; i++)
    if (b[3][i] != a[i]) b[3][0]++;
  b[4][1] = 2;
  b[4][2] = 3;
  for (i = 3; i <= n; i++) b[4][i] = 6 - b[4][i - 1] - b[4][i - 2];
  for (i = 1; i <= n; i++)
    if (b[4][i] != a[i]) b[4][0]++;
  b[5][1] = 3;
  b[5][2] = 1;
  for (i = 3; i <= n; i++) b[5][i] = 6 - b[5][i - 1] - b[5][i - 2];
  for (i = 1; i <= n; i++)
    if (b[5][i] != a[i]) b[5][0]++;
  b[6][1] = 3;
  b[6][2] = 2;
  for (i = 3; i <= n; i++) b[6][i] = 6 - b[6][i - 1] - b[6][i - 2];
  for (i = 1; i <= n; i++)
    if (b[6][i] != a[i]) b[6][0]++;
  int x = 1;
  for (i = 1; i <= 6; i++)
    if (b[i][0] < b[x][0]) x = i;
  cout << b[x][0] << endl;
  for (i = 1; i <= n; i++) {
    if (b[x][i] == 1) cout << 'R';
    if (b[x][i] == 2) cout << 'G';
    if (b[x][i] == 3) cout << 'B';
  }
  return 0;
}
