Discrete Logging
Time Limit: 5 Seconds Memory Limit: 32768 KB
Given a prime P, 2 <= P < 2^31, an integer B, 2 <= B < P, and an integer N, 2 <= N < P, compute the discrete logarithm of N, base B, modulo P. That is, find an integer L such thatB^L == N (mod P)
Input
Read several lines of input, each containing P,B,N separated by a space, and for each line print the logarithm on a separate line.
Output
If there are several, print the smallest; if there is none, print "no
solution".
The solution to this problem requires a well known result in number theory that
is probably expected of you for Putnam but not ACM competitions. It is Fermat's
theorem that states
B^(P-1) == 1 (mod P)
for any prime P and some other (fairly rare) numbers known as base-B pseudoprimes.
A rarer subset of the base-B pseudoprimes, known as Carmichael numbers, are
pseudoprimes for every base between 2 and P-1. A corollary to Fermat's theorem
is that for any m
B^(-m) == B^(P-1-m) (mod P) .
Sample Input
5 2 1 5 2 2 5 2 3 5 2 4 5 3 1 5 3 2 5 3 3 5 3 4 5 4 1 5 4 2 5 4 3 5 4 4 12345701 2 1111111 1111111121 65537 1111111111
Sample Output
0 1 3 2 0 3 1 2 0 no solution no solution 1 9584351 462803587Submit
Source: University of Waterloo Local Contest 2002.01.26