01: #include <stdio.h>
02: 
03: int main()
04: {
05:     unsigned long long au, bu, cu;
06:     signed long long as,bs,cs;
07:     
08:     au = 123456789L;
09:     bu = 987654321L;
10:     cu = au * bu;
11:     bu = cu - au*au;
12:     printf(" bu = %lld, cu = %lld\n",bu,cu); 
13:     au = (cu+au)/(cu-bu);
14:     printf(" au = %lld\n",au);
15:     
16:     as = -123456789L;
17:     bs = 987654321L;
18:     cs = as * bs;
19:     bs = cs - as*as;
20:     printf(" bs = %lld cs = %lld\n",bs,cs); 
21:     as = bs/(cs-bs);
22:     printf(" as = %lld\n",as);
23:     cs = (-bs)%1234;
24:     printf(" cs = %lld\n",cs);
25:     
26:     return 0;
27: }

Results

 bu = 106691052362444748, cu = 121932631112635269
 au = 8
 bs = -137174209862825790 cs = -121932631112635269
 as = -9
 cs = 914