Sumber Vending machine

#include <stdio.h>
#include <string.h>
#include <conio.h>

main()

{
    int money, money2, price, change;
    long int product, a, b, c;
    printf("Drinking Water Vending Machine\n");
    printf("Silahkan pilih minuman yang akan anda beli\n");
    printf("1. Pure Life\t");
    printf("\t\tRp.3500,-\t\n");
    printf("2. Aqua\t"); printf("\t\tRp.4000,-\t\n");
    printf("3. Oasis\t"); printf("\t\tRp.2000,-\t\n");
    scanf("%i", &product);

    switch(product)
    {
        case 1:
            price = 3500;
            printf("Silahkan Masukan Uang Anda!");
            scanf("%i", &money);
            if(money == price || money > price){
                change = money-price;
                printf("Kembalian Anda adalah Rp. %i\n", change);
                for(a=0;a<=24;a++){
        for(b=0;b<=24;b++){
            for(c=0;c<=24;c++){
                if((a*100+(b*500+c*1000))==change){
                    printf("100 = %i, 500 = %i, 1000 = %i\n",a,b,c);
                }
            }
        }
    }

                printf("Terima Kasih atas Transaksi anda\n");

            }
            else if(money < price){
                printf("Masukkan kembali uang anda!");
                scanf("%i", &money2);
                money = money+money2;
            }
            break;

        case 2:
            price = 4000;
            printf("Silahkan Masukan Uang Anda!");
            scanf("%i", &money);
            if(money == price || money >= price){
                money - price == change;
                printf("Kembalian Anda adalah Rp. %i\n", change);
                printf("Terima Kasih atas Transaksi anda\n");
            }
            else if(money < price){
                printf("Masukkan kembali uang anda!");
                scanf("%i", &money2);
                money+money2 == money;
            }
            break;

        case 3 :
            price = 2000;
            printf("Silahkan Masukan Uang Anda!");
            scanf("%d", &money);
            if(money == price || money >= price){
                money - price == change;
                printf("Kembalian Anda adalah Rp. %i\n", change);
                printf("Terima Kasih atas Transaksi anda\n");
            }
            else if(money < price){
                printf("Masukkan kembali uang anda!");
                scanf("%i", &money2);
                money+money2 == money;
            }
            break;
     }
    return 0;
}