function [steps] = bgiant(a, b, N, s);
%use: bgiant(a, b, N,s), baby step-giant step algorithm
%(c) 1999, Oguz Yetkin, CS638 (Cryptography)

xzero=0:s-1;
xonerange=(N/s)-mod((N/s),1)
%xonerange=N;
xone=0:xonerange;
lhs=mod(a*xzero,N);
rhs=(b-a*xone*s);          
rhs=mod(rhs, N);




lhs=sort(lhs)
rhs=sort(rhs)
%for i=1:s
for i=s:-1:1      
	%for j=1:xonerange
	for j=xonerange:-1:1
		if(lhs(i)==rhs(j))
			fprintf('x=%d\n',xzero(i));
			fprintf('steps=%d\n',i*j);
			steps=i*j;	
			return ;
		end
	end
end

fprintf('found nothing');
steps=-1;
return