begin name
tyson14
end name

begin reactions
r1 {1.0}$EXTERNAL = {1.0}R
r2 {1.0}R = {1.0}$EXTERNAL
r3 {1.0}$EXTERNAL = {1.0}X
r4 {1.0}X = {1.0}$EXTERNAL
end reactions

begin rate equations
r1 = env*k1*S
r2 = env*k2*R[t]*X[t]
r3 = env*k3*S
r4 = env*k4*X[t]
end rate equations

begin parameters
k1 = 2.0
k2 = 2.0
k3 = 1.0
k4 = 1.0
tau = 4.0
env = 1.0
end parameters

begin initial conditions
R[0] = Ri
X[0] = Xi
end initial conditions

begin initial values
Ri = 1
Xi = 0.0
end initial values

begin assignment rules
S := Floor[t/tau]
end assignment rules

begin function definitions
end function definitions

begin events
end events

begin process annotations
end process annotations

begin species annotations
end species annotations

begin units
end units