n = int(input())
l = input()
lamps = []
res = 0
colors = ['R', 'B', 'G']
for i in l:
    lamps.append(i)
for i in range(1, n - 1):
    if lamps[i] != lamps[i - 1] and lamps[i] != lamps[i + 1]:
        continue
    elif lamps[i] == lamps[i - 1] and lamps[i] == lamps[i + 1]:
        S = colors[::]
        S.remove(lamps[i])
        lamps[i] = S[0]
        res += 1
    elif lamps[i] == lamps[i - 1] and i != 1:
        S = colors[::]
        S.remove(lamps[i])
        S.remove(lamps[i - 2])
        lamps[i - 1] = S[0]
        res += 1
    elif lamps[i] == lamps[i + 1] and i != n - 2:
        S = colors[::]
        S.remove(lamps[i])
        S.remove(lamps[i + 2])
        lamps[i + 1] = S[0]
        res += 1
    elif i == 1:
        S = colors[::]
        S.remove(lamps[i])
        lamps[i - 1] = S[0]
        res += 1
    elif i == n - 2:
        S = colors[::]
        S.remove(lamps[n - 2])
        lamps[i + 1] = S[0]
        res += 1
print(res)
print(''.join(lamps))