Tugas Nilai Terbilang

#include <iostream>

using namespace std;

void satuan (int a)
{
    if (a==1){
        cout << "satu";
    }
    else if (a==2){
        cout << "dua";
    }
    else if (a==3) {
        cout << "tiga";
    }
    else if (a==4){
        cout << "empat";
    }
    else if (a==5){
        cout << "lima";
    }
    else if (a==6){
        cout << "enam";
    }
    else if (a==7){
        cout << "tujuh";
    }
    else if (a==8){
        cout << "delapan";
    }
    else if (a==9){
        cout << "sembilan";
    }
    else if (a==10){
        cout << "sepuluh";
    }
    else if (a==11){
        cout << "sebelas";
    }

}
void terbilang (int b)
{
    if (b<=11){
        satuan(b);
    }
    else if ((b>11)&&(b<=19)){
        terbilang (b%10);
        cout << "belas ";
    }
    else if ((b>=20)&&(b<=99)){
        terbilang (b/10);
        cout << "puluh ";
        terbilang (b%10);
    }
    else if ((b>=100)&&(b<=199)){
        cout << "seratus ";
        terbilang (b%100);
    }
    else if ((b>=200)&&(b<=999)){
        terbilang (b/100);
        cout << "ratus ";
        terbilang (b%100);
    }
    else if ((b>=1000)&&(b<=1999)){
        cout << "seribu ";
        terbilang (b%1000);
    }
    else if ((b>=2000)&&(b<=9999)){
        terbilang (b/1000);
        cout << "ribu ";
        terbilang (b%1000);
    }
    else if ((b>=10000)&&(b<=99999)){
    terbilang (b/1000);
    cout << "ribu ";
    terbilang (b%1000);
    }
    else if ((b>=100000)&&(b<=999999)){
        terbilang (b/1000);
        cout << "ribu ";
        terbilang (b%1000);
    }
    else if ((b==1000000)){
        terbilang (b/1000000);
        cout << "juta ";
        terbilang (b%1000000);
    }
    else if((b>10000000)){
        cout << "ERROR!!!" << endl;
        cout << " Nilai Yang Anda Masukkan Terlalu Banyak.";
    }
}
int main()
{
int nilai;
cout << "NAMA : FERRY INDRAWAN" << endl;
cout << "NPM  : 06.2017.1.06837" << endl;
cout << "APLIKASI MENGHITUNG ANGKA KE BILANGAN" <<endl<<endl;
cout << "==================================" <<endl;
cout << "Masukkan Angka: ";
cin >> nilai;

if (nilai<0){
    cout <<"minus";
    terbilang (nilai);
}
else{
    terbilang (nilai);
}

cout <<endl<< "===================================" << endl;

        return 0;
}