Hi,

In n and r are quite large so that calculating their factorial is somewhat infeasible, how would one approach to find the solution to nCr mod p (nCr stands for n choose r) where p is a prime number ?

simple example: n=17 , r= 7 p =3 answer =2;

But what if n and r are of the order 2*10^9 and 10^9 respectively and p is a prime number say 103.

Please provide some guidance.

Thanks for your patience.