Приклад. a=386, b=257, N=533.
M(a,b) -?

R=2^10=1024;
N^(-1) mod R =317.
N'=-317 (mod 1024)=-317+1024=707.

x=386*257=99202.
y=99202+533*((xN')mod R) = 
99202+533*6=102400

y/R=100
M(a,b)=100.