clear all; close all;

alpha = 0.0011;
beta = 0.03;

s(1) = 999
i(1) = 1
r(1) = 0

for t = 1:100
    s(t+1) = s(t) + (-alpha * i(t) * s(t))
    i(t+1) = i(t) + alpha*i(t)*s(t) - beta*i(t)
    r(t+1) = r(t) + beta * i(t)
end