directive duration 7000.0 points 1000
directive plot <X1 t^ X2>; <Y1 t^ Y2>; <Z1 t^ Z2>; <S1 t^ S2>

def signal(N,a1,a2) = (N * <a1 t^ a2>)

def reaction1to1(N,a1,a2,b1,b2) =
  ( N * {t^*}[a2 t^]:[b1 t^]<b2>
  | N * <t^ b1 t^> )

def reaction1to2(N,a1,a2,b1,b2,c1,c2) =
  ( N * {t^*}[a2 t^]:[b1 t^]<b2>:[c1 t^]<c2>
  | N * <t^ b1>
  | N * <t^ c1 t^> )

def reaction2to1(N,a1,a2,b1,b2,c1,c2) =
  ( N * {t^*}[a2 t^]:[b2 t^]:[c1 t^]<c2>
  | N * <t^ c1 t^> )

def reaction2to2(N,a1,a2,b1,b2,c1,c2,d1,d2) =
  ( N * {t^*}[a2 t^]:[b2 t^]:[c1 t^]<c2>:[d1 t^]<d2>
  | N * <t^ c1>
  | N * <t^ d1 t^> )

( reaction2to2(1000, X1,X2, Y1,Y2, A1,A2, B1,B2)
| reaction2to1(1000, A1,A2, C1,C2, S1,S2)
| reaction1to1(1000, Z1,Z2, C1,C2)
| reaction1to1(1000, B1,B2, C1,C2)
| signal(100, X1,X2)
| signal(100, Y1,Y2)
| signal(100, Z1,Z2) 
)