Inverse Congruential Generator
Usage: ./icg modulus multiplier adder seed
The ICG appears to work. The major issue at this point is that the mod_inv() function only works correctly for signed long longs, as the Bezout pairs can sometimes be negative. This property means we can only have signed long long inputs, which reduces our input space from 64 bits to 63. It'd be nice if that weren't the case.