def hitungNomorBit(angka, nomorBit):
    # Mengonversi angka menjadi biner sendiri
    binary_string = ""
    if angka == 0:
        binary_string = "0"
    else:
        while angka > 0:
            binary_string = str(angka % 2) + binary_string
            angka //= 2
 
    # Cek posisi nomorBit, jika lebih dari panjang biner, return None
    if nomorBit >= len(binary_string):
        return None
 
    # Menghitung jumlah bit '1' dari kanan hingga posisi nomorBit
    return binary_string[:len(binary_string) - nomorBit].count('1')
 
# Contoh penggunaan
print(hitungNomorBit(13, 0))  # Output: 1
print(hitungNomorBit(13, 1))  # Output: 3
print(hitungNomorBit(13, 2))  # Output: None

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