#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING

#include <bits/stdc++.h>

using namespace std;
char a[] = "BGR";
const int N = 2e5 + 50;
char str[N], ans[4];

int main() {
    int n;
    scanf("%d%s", &n, str);
    int ansc = 0x3f3f3f3f;
    do {
        int cnt = 0;
        for (int i = 0; i < n; i++)
            if (str[i] != a[i % 3])
                cnt++;
        if (cnt < ansc)
            strcpy(ans, a), ansc = cnt;
    } while (next_permutation(a, a + 3));
    printf("%d\n", ansc);
    for (int i = 0; i < n; i++) putchar(ans[i % 3]);
    return 0;
}